Need Help With Picking Parts

I've never built my own rig, but have wanted to for a while and I'm a little lost. I would like to stay under $1,200 and from newegg these are the parts I've picked so far.

CPU -Intel Core 2 Duo E8400

MB -GIGABYTE GA-EP45-UD3P

PSU -CORSAIR CMPSU-650TX 650W

GPU -SAPPHIRE 100282SR Radeon HD 5850 1GB

HD -SAMSUNG Spinpoint F3 HD502HJ 500GB

RAM -G.SKILL PI Black 4GB

Case -NZXT Apollo

Any advice on parts I should scrap or upgrade would be really appreciated.

Do you live near a microcenter? They sell i7 920s for cheap.

Turn the Cpu to an i5, motherboard to an p55a and i think you'll do fine.

Making the changes suggested, this is what my parts list looks like now. So everything should work together or did I make a mistake in picking any of the parts? Also, as far as the OS what should I get? I figured I'd go with Windows 7 but looking at the different versions made me unsure. The full retail is a lot more than the OEM, is there a reason to go for one or the other?

Case- Antec 900

HDD - SAMSUNG Spinpoint F3 HD502HJ 500GB

CPU - i5-750 Lynnfield

GPU - Radeon HD 5850

PSU - CORSAIR CMPSU- 650TX

RAM - G.SKILL 4GB DDR3 1600

Mobo - GIGABYTE P55A UD4P