Here's what I've used in my first homegrown rig.
Corsair 800D Obsidian case
XFX 750W Black Edition PSU
ASUS Rampage III Extreme Mobo
i7 - 930 CPU OC'd to 3.6 Ghz
EVGA GTX470 Graphics Card
12Gs (6 x 2Gb) Ocz DDR3 Gold Series DRAM (Can't remember the speed rating but it works)
2 - 1Tb Black Caviar Drives set up in Raid
1 - 850 Gb Seagate Drive-Storage
1- 650 Gb WD Drive-Storage
LG BD Rewriter
And water cooling system made up of DangerDen and Swiftech parts off the shelf.
Windows 7 Home Premium
I actually started to upgrade my HP that I bought last year and I just kept buying more stuff every week until it turned into a different computer. I wanted to go with the new i7 processor which meant a new MOBO, and that didn't fit the case I had. Then I had all these empty memory slots to fill, and the dinky graphics card I had didn't look good thru the window, then I found that my PSU wasn't big enough. Then all this stuff started getting hot when I found the overclockers website... And I went right by a Microcenter on the way home everyday... All's that I have left is the HP2408 monitor from the original computer. I already have a list of stuff I want to add and change to this one. It's turned into an addiction!