New Computer. Help?
 

Hello. I'm in the works of building a desktop which will be used mostly for gaming and such. Much help would be appreciated.
My current thoughts are:
AMD Phenom 9550 vs AMD Athlon 64 6400+
MSI K9NGM4-F Motherboard
160 GB Hard Drive (As Requested)
GeForce 8800 GT Video card (As Requested)
and 3GB DDR2 6400
DVD +/- RW
All Running on Windows XP

What Processor would be the better fit? Or are there any other suggestions?
Is the motherboard fine?
I heard that XP can only utilize up to 3GB RAM, is this true?
How much power would I need for this?
What kind of cooling should be used?
Any other suggestions?

Thank you

Not sure about some of the questions, but yes, it's true that if you use an x86 operating system, it'll only support ~3gb of RAM. If you use the 64-bit versions of XP or Vista, you should be able to support more, though I'm not sure what the limits are. Most mobos only support up to 4gb anyway.

Then again, with the x64 systems, you apparently still have a lot of compatibility issues, because of the whole 64-bit thing.

Buy an Intel processor.
Buy something with a P35/P45 chipset in it.
Windows XP is fine.
You need arond 550W. Don't buy cheap unbranded PSUs. Channel Well Tech or their rebrands are good.
You need a heatsink for the CPU and some fans on your case.

160 GB hard drives are ancient, you'd get better value for money with a 500 GB.

Newegg's even got a 750GB on sale for $99 today.