Here are some screenshots which I made on that machine, one is with CPU-Z and GPU-Z and rest is from 3DMark03 and 05:

The case is interesting with the hot plug style drive bays.
If you really want to make it a rocket, install Window 98 and make it scream 😀

I try 98 and I make 3dMark tests to compare it to XP, I have drivers for mainboard chipset for 98 😀 Can I use in 98SE SSE2 instructions in games and in programs ?

EDIT: I installed 98 on another harddisk and I when I do that I put out one 512 Mb RAM stick and I run 3DMark2001 in 98 and in XP and in XP I have better score so my rig is more like rocket in XP, I see also 98 is slower on that rig than xp, even folders opening are slower in 98, and I stay at XP because I also want to play games from GoG and they installers don`t run on 98. Here is 3DMark2001 screenshots:

I rebuild that rig to new specs:

Motherboard: ABIT NF8
Processor: AMD Sempron 2800+ 1.6 Ghz but without 64bit extensions
Memory: 2x 512 MB DDR400
Harddisk: Seagate 200GB IDE
Videocard: ATI Radeon 9550U (400/400)
Opticaldrive: LG DVD-ROM
USB 2.0 card on VIA chipset

Now that rig is far faster than with PIV 2.0, even Gothic 2 run smooth now, before that game slowed down much times at playing.

and here is photo:

Is the Logic PSU any good? I never heard of the brand, but usually that's a sign I need to take a second better look before using it.

I have more than two years that PSU and I have everytime good voltages, all that time I don`t have any problems with him, that`s little cheaper PSU but in my opinion is good. Logic produces also other things like cases, that company is from Taiwan. Here is link to that company so you can see what they producing. I have even wireless mouse from Logic and is good for me, sometime ago I have problem with that and that company easy replaced that mouse on warranty without any problem, but now works for more than year very good.

When I checked voltages at Speccy program I see:
+3V 3.29
+5V 5.08
+12V 12.09
so you can see they`re good.

Is that a Voodoo 3 in the one pic?

Sticking with XP is the right choice if you're using the Radeon card. Why not choose a 9800XT if you're going to use a Radeon? With the system you've got, it would be a huge performance increase. Even a 9600XT would likely be a pretty big boost, and you can use passive coolers with those.

No, I even don`t have Voodoo3 now, that`s Radeon 9550U with 400/400 clocks, you can see information on that card on one screenshot with GPU-Z, and that MD5000 board can`t use AGP 2X cards, also ABIT NF8 can`t do that, and I stick all time to XP because that`s rig is for GoG games and Diablo II/Gothic 1-2. In future I buy better Radeon or some mainboard with CPU on AM2 socket, I plan to use AMD CPU and videocard. I used Intel and NVIDIA for years and I want to return to AMD 😀