Did the exact same thing here.

Had a tired P4 2.8G with 2gig of Ram

I got an MSI P35 Neo2-FR motherboard, a Q6600, an Arctic Cooling Freezer 7 Pro heatsink, a PNY Geforce 8800 GT 512mb, and OCZ 4 gb ( 2 x 2gb ) PC2-6400 C5 for £523.

You need a GOOD PSU to run those things ( something at the 500 Watts + range ).

And you will need to reinstall windows afterwards.

I'm not the hardware guru I used to be - but I'd read a lot about the Q6600 overclocking well. It's 2.4Ghz by default. I just clicked up the FSB in the Bios to run it at 3Ghz - and it's been running perfectly at that speed without any other tweaks whatsoever, for a month solid - rendering animations etc. I run a Dell 24" and my old Hitachi 19" TFT's from it. Amazing rig. The only thing I would now change is the fact that I run a 75 Gb WD Raptor system disk - I'd quite like to switch to a newer 150 Gb WD Raptor instead.

That - and stupid Photoshop being a 32 bit app.

Doug