Re: Upgrading questions
I couldn't find what PSU that system uses, so I wouldn't be able to tell you if you need a new one.
For your ram, just make sure it's DDR and is 400Mhz, so if you can find a stick with those specs anywhere cheaper than the site you linked, grab it. It'll be supported by your system.
To be honest, that system isn't that great. You can build a much better system for $500 (excluding monitor and OS). I'd suggest buying some new core components (Cpu, gfx card, mobo, psu, ram, hdd)
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