Quote - [Vista and Win7 'use' more memory when idle because they are making use of that memory for pre-caching. It is a good thing that helps the system, not a bad thing.

Go with Windows 7 64 bit. It'll make better use of the available RAM and 64 bit capable CPU, allow more RAM to be used and will be ready for Poser Pro with its 64 bit capable renderer.

XP x64 is effectively dead now. Would be a pointless recommendation over Windows 7 x64

XP is not dead. Windows 7 is better than Vista, but it's still too large for home users. Don't believe the hype. They're selling a new product. They want your money.

And of course Vista and 7 are not better in use of RAM on Laptops and PC IF THEY DON'T HAVE QUAD CORE PROCESSORS - they're slower. Read some benchmark tests that indicate just that. And again: Windows 7= 20 GB of your HDD, XP less than 5 GB. On a laptop with the average HDD of 200 GB that makes a difference too. Why spend money on a quad core processor AND Windows 7 to gain from the advantages that Windows 7 offers?

And as always with Windows: it's better to wait until it comes with SP2, until then they hopefully find a way that the 'search' process in Windows 7 alone doesn't need more than 500 MB of RAM. This is ridicilous and it was already bad in Vista.