I just read an interesting explaination on why Window 7 for SolidWorks 2011. Below are the reason:-

– Windows 7 x64 is a true 64-bit implementation (Windows XP was originally introduced as a 32-bit operating system)

– Microsoft® removed a crucial threading lock, which allows up to a (approximately) 30% increase in performance on some hardware.

– You’ll see 20% – 30% improved battery life on laptops with Windows 7.

– Windows 7 is smarter about memory handling, and paging is more efficient– SolidWorks development work is done on Windows 7

– XP is no longer supported by Microsoft

Between Vista and Windows 7, Windows 7 has a smaller memory footprint, and has improved graphics resource handling with multiple windows. Both of these improvements have a positive impact on SolidWorks.

If you are looking forward to upgrade your hardware and OS, i bet you have no reason not to buy Window 7.