My first home build-advice needed please!!!

Hi, I've never built a PC before and after many hours of research through forums I have come up with what I hope is a good build for gaming.
I don't really want to spend too much on my first build so this is it:

Corsair TWIN2X4096-8500C5DF 4GB (2x2GB)

Antec Nine Hundred Case

Intel Core2 Quad Q6600

HIS Hightech ATI HD4850 625Mhz

Asus P5Q PRO Motherboard

Western Digital Caviar 640GB WD6400AAKS

Antec NeoPower 650W

ASUS DRW-2014L1T 20X DVD±R/RW SATA LightScribe


I'm hoping to attempt overclocking but am worried about failing on my first try.
Will my power supply be sufficient and just generally, will all my components work well together for gaming?
Any advice would be greatly appreciated.
thanks

Ahhh ok thank you for your advice i'll look into a CPU cooler and will read the ocing threads. Do you think my build will be good enough for gaming?

Thanks alot, you guys are really helpful
I'll get the cooler, just another question i'll be using a sumsung 275t as my monitor do you think my graphics card is good enough?

Intel LGA775. If you decide to use the Xigmatek s1283, spend a few dollars - about $6 - to get the back mounting plate. The S1283 uses the Intel pushpin HSF mounting system. Many of us (most?) do not like the Intel mounting system. The mounting plate gives a more secure mount, especially for something that is substantially larger than the stock Intel HSF.

Military axiom: "There's no such thing as a stupid question."
John's (me) Corollary: "Better a stupid question than a stupid mistake."

And remember, we were all noobs at one time.