Unfortunately XP is no longer available with new PC's.
Extrremes Camapaign's CORE causes in Windows7 Extremes to close while teleporting to a new Environment in Both SS2008 and Extremes. Single Environmet Missions within both programs works fine. I completed the first two Campaigns on a less powerful PC with XP installed, with very few problems.
I am currently running a 16 Core Processor with a 3.2 ghz Processor with 2-1TB HD's 4GB Memory and a 4 GB NEIVDA Video Card. Frame rates are constantly 65+fps.
I tired running XP on the 2nd HD, but Microsoft won't allow it to be connected to the same Computer. That could be done earlier before VISTA was released. Since Windows 7 is an update to VISTA, that is no longer possible.
Alex