Sry, but your friend is by himself a kind of a PC-Noob:
RAM:
Your rig will run a q6600 (get one with G0 Stepping), but only 667MHZ RAM, get at least 800MHZ. Thats the point where the your friend failed, I guess he is choosing the components by price - higher the better and thats the wrong approach. As someone mentioned before, there is no point to get a Quadcore, but they are cheap, so go for it.
Second is the Size: to use 4GB RAM you need a 64bit OS, 32bit OS will only adress 2,8 - 3GB (with some tweaking, without it will only adress about 2GB). I guess you will install Vista, as your gonna buy 4GB RAM you need the 64bit Version, if you want to use the whole 4GB and I can tell you PR will not run on 64bit Vista nice and smooth - no it won't run at all.
Power Supply:
You will never ever need a 750W power supply, this is total overkill and the only thing you will get out of this, is a high eletricity bill. Get a Corsair 520W power supply. That will fit your specs well.
Mainboard:
If you don't gonna plan to overclock your System the x38-DS5 is also overkill and as you said you are don't know much in this sector, i guess u won't do much overclocking. So a P35-DS4 will do it very well.
GFX
The 8800GTX is a good card no doubt, but the 8800GT is overall about 10% behind the GTX and costs half the price. So I would buy a 8800GT instead of the GTX. Get the cheapest one, they are all the same (Foxconn is building the PCB and NV the Chips, all the producers like Gainward, Sparkel, etc. are doing is sticking the parts together and label it).
Display:
In the price sector of about 300$ the HP w2207h is a very very good choice, so i would recommend this one. And if you have that much money to spend on a pc, don't buy high-end components without a good display, what's the need of all the stuff, if you can't see it well. When you are willing to spend more money on a display than 300$ look for a 24" Dell.
Case
That's a matter of taste, but 180$ for a case. I don't know if its worth it.
CPU-Cooler is missing! Get a Scythe Mugen or a IFX-14 if it fits in your case.
For the money you will save get a X-FI (not the X-FI extreme audio) and invite your girl friend for dinner. No, you will save so much money you can take her for a weekend to hawaii.

If you don't wanna be kind to your girlfriend buy a 7.1 or 5.1 speakerset from Teufel, Logitech or Creative.
And if you plan only to play PR, this rig is way too much.
Again: the high priced components aren't always the best
If you still plan to buy that rig, that your friend told you too, buy at least faster RAM.