Am looking to upgrade my psu/videocard/HD..need advice

So..its been a few years since I upgraded my desktops...now looking to upgrade my latest one...specs are here...my case in a mid ATX as stated

http://h20000.www2.hp.com/bizsupport/TechSupport/Docume...

I was looking at a 450 watt power supply..I called HP..but they said I could use a 420 at best...
I was looking at Raptor 10k harddrive..my old drive is SATA based but am not exactly sure what would fit in the slot in its place (with Windows Vista 64bit installed as I dont have any CD)
I was looking at a nice graphix card...2gbram DDR5 or 2gb at DDR3 ram/speed

Thoughts..

Thnx
SmallTank