I just got prompted today for a survey on what most gamers use as their gaming PC. Very interesting results:

http://www.steampowered.com/status/survey.html

A few notes:
1) Most peope are still in the ATI 9600/9800 ballpark. Hmmm... now this is interesting. I do not feel that outdated anymore with my 9600 XT. Also, the most common NVidia card seems to be FX 5200 series. An antique type of card (if you ask me) but, hey, that's what most people have.
2) Memory seems to be eithyer 512 MB or 1 GB. Not a surprise here.
3) AMD Processor speed - between 2 and 2.29 GHz. Keep in mind that an Athlon64 3000+ is around that numbers... (2200 MHz if I remember correctly)
4) Most machines are now upgraded to XP SP2 (73%). The XP SP1 percentage is around 13%, and XP RTM is just 7%. The Windows Update team did a good job :-)
5) Wow - with almost 90%, NTFS rules as the dominant file system! Congrats to the NTFS team (Neal, Molly and others - you know who you are!). FAT/FAT32 is now history.
6) There is an interesting distribution on the free storage space. If you draw the "free space" distribution histogram, you see a growth p to about 20 GB, and then a nice exponential decrease. The max is around 20 GB. And the next picture shows what most people use 80 GB harddisks. This, correlated with the previous distribution suggest a 75% average space utilization, and 25% free space. Very interesting data.