Love the challenge!
Did my Y2K "monster" build a bunch of years ago now and its still rockin hard.
I used the same rules you have except the blue one =).

So in my mind I already see a Hercules GF2U on some Gigabyte i815 board.
Not sure if there's blue memory, perhaps one of the brand names had some.
Sound card will probably be easy, I'm sure Hercules has you covered there too.
And I cant remember if any other cases then the Cooler Master ATCS cases that qualify, when did Lian-Li become popular? a few years later?`

Anyways looking forward to see what you come up with!

1. Case
A few years ago, back when my early plans still involved building the machine around a Thunderbird 1400 and a Hercules 8500, I discovered the Lian Li PC-60 and wanted to own one for a long time. This is how original PC-60 non-usb from 2000 looks like. Notice the square piece of plastic around the button, later cases don't have it

(source: dansdata)

That changed when I came across the Cooler Master ATCS cases — after that, I completely forgot about Lian-Li. Which one is better and which one someone prefers is purely personal preference. As for me, I remain on the CM team : )

I could write a separate essay about ATCS case here, but I will focus only on the most important ones.

In the year 2000, excluding server and HTPC cases, the following ATCS models existed: ATC-100, ATC-200, and ATC-201. These models are relatively well-known to anyone who has been into old PCs for a while, but with the ATC-200 and ATC-201 you need to pay attention to the fact that there were two versions of each. The first versions are from the year 2000, and the second ones from 2002. I’ve encountered at least one thread where someone was working on a “millennium build” but had a 2002 version of the case. It’s also worth mentioning the Praetorian PAC-T01, which was an evolution of the ATC-201 and came out in 2005. As for the ATC-100, as far as I know, only one version existed. That case uses a 120 mm side-mounted fan with a duct directing airflow toward the rear panel, and because of that I didn’t consider it. It's about future plans related to the installation of the glass.

A small side note: there’s an infographic floating around the internet proudly claiming that the ATC-100 was the first aluminum PC case for a home computer in history. To this day I haven’t been able to find any source confirming this claim. If anyone has reliable information about this, I’d be very grateful : ) (Completely ignoring the fact that in the photo we see not an ATC-100 but an ATC-210 from 2001..)

The visual differences between the 2000 and 2002 versions of the ATC-200 and ATC-201 are as follows:

• The 2000 versions have a removable top cover under which the fan screws and a "hole" for inserting the power supply are located. Because of this, the side panels from the 2000 series do not fit the 2002 revisions. The 2002 cases have the fixed top, and the PSU is installed from the rear.
• The 2002 versions use threaded motherboard standoffs, whereas the 2000 versions use press-fit standoffs that snap into square holes in the motherboard tray.
• The 2002 versions have just a hole for the rear fan where you attach a grill, while the 2000 versions have a stamped/cut-out pattern and do not require a grill. There’s also an additional cut-out pattern near the expansion slots.
• On the 2000 ATC-200, the mesh front panel reaches all the way to the edges of the case, whereas in the 2002 revision it is the same as in the ATC-201.
• On the 2000 versions, the motherboard tray and expansion slot covers are not actually aluminum — a magnet test confirms this 😀 The 2002 tray is aluminum and is also much more rigid.
• There are also minor differences in the PSU cage design, which will turn out to be crucial later in the story.

Availability
To figure out how difficult each case (2000 "pre-facelift", ofc) was to obtain, I looked at the number of available online photos, archive listings, etc. My conclusion is as follows: the ATC-200 is the easiest one to find, and that’s the one I started hunting for. I found photos of the ATC-201 on only two websites, in very low resolution. There were relatively many photos of the ATC-100, and they appeared more recent. The black version, however, is another story entirely — a German collector claims that after years of searching he never once came across a black ATC-100. (He has all atc`s without black atc-100 and pre-facelift atc-201

And after 3 years of hunting ATC-200, i scored this: "Pre-facelift" Cooler Master ATC-201-SX

I don't know if anyone will share my opinion, but this removable top makes impression that this case comes from the PIII era. In the first 5.25" bay you can see a different shade of the drive cover, because it comes from a PAC-T01-E1 — a model five years newer — and it was installed only for the photos. The case arrived with a full set of four factory YS-Tech ball-bearing fans. The fan markings aren't visible in photos from old reviews, but you can guess they're original because later versions had a 3-pin connector. These fans have a Molex. As I mentioned earlier, unlike the facelifted 2002 model, it turns out that the motherboard tray is, for some reason, not made of aluminum. Fortunately, the zinc coating is thick, and I’m hoping it won’t start rusting in the future. The slot covers are also steel. Unlike the ATC-200, this chassis has one additional 5.25" bay and features two front USB ports. The case arrived with a box containing all the original screws, standoffs, and the motherboard I/O shield still in protective film.

Proof

The oldest mention of this case comes from July 2000, from the archived Cooler Master website, which interestingly references two color variants — silver and black. The black version is missing its product image. I know that the "SX" marking means black color, because the black version of the ATC-100 is described in the same way on their website. In the December 2000 capture, the black version’s graphic was removed entirely.

Another mention comes from September 2000 on the AnandTech forums, where users were trying to find anyone who actually owned the case. One user mentioned that the manufacturer had told him they were experiencing a “shortage” and that the cases wouldn`t be available in November. I’m not able to determine whether this was a pre-launch shortage or whether the first batch had already reached end users, but based on the GAMEPC review from December, they weren't.

The final, definitive proof comes from another AnandTech thread, in which, in December 2000, a user confirms receiving the case and expresses excitement about it (the same excitement I’m feeling — 25 years later).

I admit that December is the upper limit of my assumptions. This was also one of the reasons I considered the ATC-200, as its proof date is from mid-2000. However, I couldn't ignore the condition of the case and the fact (which 99% of users will agree) that it looks much, MUCH better.

I'm including saved webpage screenshots in PDF format as an attachment to this post. I highly recommend reading the revelations about how aluminum housings better cool components because they conduct heat better xD

The writeup on the case was a great read. I'll be watching your progress with great interest.

That case is so sexy it makes LianLi's look kinda basic!

2. Power Supply

I don’t remember exactly how I began searching for information about power supplies from the year 2000. I paid particular attention to the Enermax EG-465P and its derivatives because they had gold fan grills. Unfortunately, the earliest reviews I found were from 2001.

I browsed eBay and various reviews looking for a power supply that would be in some way unique — there were models in gold, blue, or with a galvanized steel housing that looked deceptively similar to aluminum. Of course, there were also fully aluminum units. However, all of them came from 2001 or later.
I wanted to completely settle the matter of the case and power supply, so in the end, only two models from the year 2000 remained on the battlefield:

• Enermax EG-351P-V(e) — March 2000
• Enermax EG-451P-V(e) — October 2000

The first delivers 32A on the +5V rail, the second — 44A. Because of that, the 451P would have been the nicer option. However, it had one crucial issue — availability. Although photos of it were floating around online, despite long eBay monitoring I think I came across only a single unit, and it was in very poor condition. The 351P, on the other hand, was relatively easy to find.

In the end, I purchased the EG-351P-V. Even though one might think the 451P would be nicer option beacuse of beefier 5V rail, the 351P has one major advantage — unlike the 451P, it does not have a P4 connector, which makes it a much better match for the components it will be powering.

Purchased at a good price as untested, in very good cosmetic condition. That didn’t bother me, because I was planning to refurbish it anyway. After it arrived, it turned out to be fully functional, and not a single capacitor inside was bulging, which suggests it hadn’t been used for long. It features an interesting function - a cable with 3-pin connector with sense cable only, that allows you to monitor the RPM of one of the fans. This, enables automatic emergency shutdown of the computer in case of fan failure. ATX20 cables are factory-sleeved, which would indicate that sleeved wiring existed already in the year 2000 😀
It’s also interesting that this PSU has something I haven’t seen in any other unit — not even modern ones: the Molex connectors are gold-plated. This really adds to the impression of dealing with a high-end product. 😀

Refurbishment

With help from the German forum Hardwareluxx, I managed to select capacitors and optocouplers according to the original specifications. The power supply is old enough that its design did not include any Low-ESR capacitors. I tried to choose replacement capacitors so that their ripple current rating was at least as high as the originals. One forum user mentioned that the ripple current shouldn’t be too high either, but based on my understanding of ripple current, I don’t really know what impact that would have. In any case, the final capacitor selection looks as follows — only Japanese brands were used.

I’ve seen various PSU restorations done by users on that forum, and I have to admit that this one is exceptionally easy to repair, because the components are not densely packed and are easily accessible.

Next, the bearing in one of the fans was replaced, because it was making a bit of noise.

After installing the power supply, I did two more things. First, I moved the sticker so it would align properly with the window in the PSU cage. In its original location, the center of the sticker was half-covered, and it had been applied slightly crooked from the factory.

Second, as I mentioned in the section about the case, it is old enough that the designers clearly didn’t anticipate power supplies with a bottom-mounted fan. At the time, the standard was still PSUs that pulled air in from the 5.25" drive side. Because this PSU doesn’t recess the fan grill into the housing the way later models do, the grill collided with the PSU cage, preventing the unit from being mounted straight. I solved this trivially — by attaching the fan grill from the inside.

I don’t have the knowledge to test the PSU in a proper service-level manner, but I can monitor the voltages. For the 5V rail, I’m getting 4.99V at idle and 4.97V under load, so the output is stable and almost perfectly centered within the spec (the ATX standard allows 4.75–5.25V). I also checked the temperatures of the PSU components under load. The hottest spot is one of the coils, to which the temperature sensor is attached, and it reaches around 45°C. Everything else, including the heatsinks, runs cooler.
For comparison, I disassembled the previous power supply I had been using to run my hardware for the past few years, and several of its capacitors were reaching temperatures above 70°C. So I’m confident about the condition of the PSU after the overhaul.

Proof

I have two pieces of evidence: a review from pcstats.com from March 2000, and an email from Enermax support stating that the first digit in the serial number indicates the production year of the power supply: 0 for the year 2000, 1 for 2001.

I'm including saved reeview webpage in PDF format as an attachment to this post.

By the way, if I upload a screenshot of a website that may still exist, the contents of the PDF file aren’t technically my own. So what kind of license should I choose in that case?

You have set yourself some very strict rules.
Most period builds are simply if that bit of hardware was available in the year of choice Not the actual manufacture date.
And don't think anyone will criticize you for not using Velcro, screws, etc that aren't dated!

I wish you luck on your build, it will be interesting