photonboy :
2004 actually.
https://www.asus.com/Motherboards/P5AD2_Deluxe/
*There are drivers for Windows 8.1 here, so it's quite possible that Windows 10 will also work. I also see some BIOS updates that may be required. Latest is 1008.009
(You may also like something like Linux Mint which may be a better choice for an older PC)
Still doesn't change the point that the mobo is much newer than 2000
Also, the 925X platform whitepaper only came out in Nov 2004, so I assumed board was probably purchased in 2005
As for Win 8.1 compatibility, like I said it depends on the CPU. If the CPU doesn't have NX bit, no Win 8.1 or 10 (and 7 runs in reduced performance). For example,
http://ark.intel.com/products/27472/Intel-Pentium-4-Processor-560560J-supporting-HT-Technology-1M-Cache-3_60-GHz-800-MHz-FSB was one of the best CPUs at the time and it didn't have NX bit.
After CPU though, the next big issue is the graphics card, and there you WILL see incompatibility with all graphics cards (i.e. no drivers) on Win 10 (unless the card was upgraded at some point to a tesla based one), and might have issues with Win 8 if he's using something like a nvidia 5000 series or ati 9000 (maybe the next series after that too, I forgot when they dropped support)