Quote - > 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.

I said XP64 not XP (32)... 

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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.

What do you mean "still too large for home users"...?
I don't believe the hype that's why I've been using the beta since February and the RTM since June... I base my opinion on my experience.

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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.

Sorry but that is just incorrect. Yes they are better at using RAM than XP, much better and you don't need a quad core to make use of them. 

Quote - 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.

 So what's 15GB? Would have thought anyone doing anything serious on a laptop is going to have at least an external drive as well. Drive space is cheap.

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Why spend money on a quad core processor AND Windows 7 to gain from the advantages that Windows 7 offers?

You don't need to. The original poster was asking about a new machine, makes sense to go with the current best x86 OS available - it'll come with an OS whatever is chosen so the cost is the same either way - actually, the current retail price of 7 is cheaper.

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And as always with Windows: it's better to wait until it comes with SP2,

Then you'll be waiting a loooong time then

Quote - the 'search' process in Windows 7 alone doesn't need more than 500 MB of RAM.

It doesn't. If it does on your install then you've got something going wrong there.