Gaming PC for WOW

I appreciate any help that can be offered. Im a complete illiterate when it comes to building computers and or what parts to use. I wouldn't even be attempting it except I keep reading it's far simpler than it sounds. Beyond some minor general use (such as surfing the net, online tv at times) this computer would primarily be built to play wow. Don't play cd's. The build I found on one forum suggested the following specifically for WOW. I only dont post the website because I'm not certain if it would violate TOS.

Specifically the following

Intel Core i3-2100 Processor 3.1GHz ...

GIGABYTE GA-H61M-DS2 LGA 1155 Intel ...

Kingston Technology HyperX Blu 4GB 1...

Seagate Barracuda 7200 500 GB SATA 6...

Asus 24xDVD-RW Serial ATA Internal O...

NZXT Technologies Source 210 Compute...

Corsair Builder Series CX V2 500-Wat...

EVGA GeForce GTX560 SE 1024MB GDDR5 ...

Windows 7 Home Premium SP1 64bit

In particular my questions are, does this include everything a computer would need to do the above stated. Im not even ceratin a modem is included in this setup. Also, I still have my windows xp disk, would that suffice for my purposes, at least in the short term? My budget is limited and I'm trying to keep it as close to $600 as possible. Finally any alternate parts suggestions? Does it need more cooling and if so what?

Thank you in advance for any help you can offer