Best os for new build super desktop

Don't know why you posted here, you're in the wrong section for this question. Try posting here:-

http://www.tomshardware.co.uk/forum/forum-13.html

To answer your question - if you're still using XP then you really should move with the times. Microsoft generally only offer 5 years of mainstream support of their operating system products with an additional 5 years of extended support. XP mainstream support did get a 2 year extension but it ended in 2009 with extended support scheduled to end in 2014, after which time it will feature on MS website just like Windows 2000 does ... in other words it will be as if it never existed. You would be very silly to invest in a new system designed around Windows XP, aside from the fact that its prevelance respresents one of the biggest security concerns for IT pros.

XP was designed alongside the type of internet functionality and security issues of 10 years ago - it was released in 2002. Do yourself a favour and move on.

W7 ultimate 64 bit (HP if you are on a budget, but you will be limited to 16GB of RAM). There are games that don't run in DX9. Gaming machine as of now should use OS that supports DX10/11 (Vista/7/8).