What operating system to use with a new rig?

[timholt]

Hmmmmmmmm, food for thought - thanks. The guy building it (nothing set in concrete yet, still waiting for a quote) is a retired ex RAAF guy who works from home.
I was put onto him by someone who had one built for him and was happy with it.
I will check out the website you provided for pre built systems.
At the moment I am running;
Thermaltake Soprano Case
Thermaltake 750w Silent Pure Power
240Gig capacity
Asus P5N32-SLI-SE-Delux
4 Gig DDR2 800 HZ Kingston memory (but can only utilise 2.something because of Windows XP Home)
Intel Core 2 Duo E6600 2.4GHz CPU
Gigabyte PCI-E 1GB 4870 video card
Creative X-Fi Extreme Music sound card
LG DVD Drive
Liteonit CD Drive
with Widows XP Home Edition
Would it be a worthwhile option to replace whatever need replacing in this set up and installing Sys 7 64 bit to get it to play Rof and IL2 CoD at a reasonable level?