This is actually a mix of parts waiting for what will become my final WinXP PC and what I have gotten for free.

Its all based around a Asus P5KPL-AM Motherboard.
This motherboard started life as a "CCTV server" running WinXP x64 and in a nice looking but nothing special case.
The HDD had failed in 2012 so it was decided to upgrade the whole CCTV system at the time and I scored the PC and starting using it at a daily driver replacing my HP D510 P4, which was now struggling with internet browsing.

Few months later, same customer different location same story, failed HDD, new system, I took the PC home. It also had the same motherboard, CPU, RAM but came in a Antec 300 case now used for my P2B-DS build. Both of the cases can be seen in that PC's post.
Asus P2B-DS Build

At some point I swapped the CPU for a Xeon x3320 2.50Ghz pulled from a dying single socket HP server. It replaced a E5200, so really no gain apart from bragging rights but hey, it was free!

It was left as is until 2014 when I got into Farming Simulator 2013 in a big way and the on board video wasn't up to the job.
Over 2014, 2015 It was upgraded to what it is today.

M/B: Asus P5KPL-AM (Free)
CPU: Intel Xeon x3320 2.50Ghz (Free)
RAM: 2x OCZ PC2 8500 5-6-6 DDR2 2GB (Purchased 2nd hand specify for this build)
Video: ASUS GeForce GTX590 (Got 2 of these in a good deal but M/B doesn't support SLI)
Audio: SB X-Fi Titanium Fatal1ty Champion with front bay (Will end up in my Ultimate XP build)
Audio Bay SB X-Fi Titanium Fatal1ty Champion
FDD: Gotek with Siverstone SST-FP55S bay converter (the screw less drive bays don't work with most converters, this isn't ideal but better then most)
HDD: Hatachi Deskstar 500GB (Free from work)
HDD: Seagate Barracuda 500GB (Free from work)
DVD-RW: iHAS122 SATA CD-RW (From the CCTV PC)
Heat sink: Noctua NH-U14S with 2nd Noctua fan (Purchased New)
Fan Controller: AeroCool X-Vision 5-Channel LCD (Waiting to go into my P3 builds)
PSU: Corsair AX1200 (Purchased 2nd hand, swapped 2 weeks ago for a new Corsair RM750i
Case: Corsair Obsidian 650D (Purchased 2nd hand for the XP build)

Recently the power supply in the P2B-DS started playing up. Maybe I was overloading it but don't think so? anyway 1200w should be more then enough.
This PC is more then happy with a 750w but shouldn't have bothered with the "I" as Corsair's software doesn't support XP, Oh well I'll swap it out one day.

The other thing I have to say is how great Noctua's support is. You need to get the "LGA1366 & LGA775 Mounting Kit" separately but they will send it out FREE if you send then your invoice and a picture of the motherboard. My original was lost in the post so they even sent a second kit, after which the 1st arrived.

I mainly use my laptop as my daily driver and this is now mainly used for games and the occasional typing up a word doc. I'm still waiting on a good price for a 2 socket motherboard which I want as my final XP build but this is filling in just fine for the time being.

Front view (and my poor camera work)

Side view, and can see the all important X-Fi and GeForce light up

Inside view, As you can see small cooling mod. I've stolen 2 fans from a 2nd 650D case and now the Video card peaks at 70/80c when playing Farming Simulator (probably the most demanding game) and sits round 40c at idle