Quote - Vista is ok to use BUT you should check out www.blackviper.com/ following the "Safe" advice will speed up Vista & make it run more stable than it will out of the box. I've used the guide on that site for every version of Windows & never run into any problems sticking to the Safe path.

Ps disable Aero & go with the XP look as it runs faster.

Nope, do not follow the advice of that site. It is a waste of time and can only give you potential problems. Stopping services is a waste of time. If they are not used they take a miniscule amount of RAM, if they are used then you need them.

Quote - If you're on a PC and do nothing Windows 7 needs 600-900 MB RAM while XP needs only around 300 MB RAM.

Memory is there to be used, unused memory is wasted memory. 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