Case: Raidmax Astro. $35. It's cheap, but it works, has decent cooling, and it even has a side window
Your choice of colors (black, green, blue, and they might still have it in beige if you're boring
)
Power supply: Sparkle, 400W minimum. Sparkle makes incredible PSU's. They last forever.
Mobo/CPU: Go with Halx's choice. DO NOT let your friend use Arctic Silver on the chip - it will cool the chip better, but it also voids your warranty for no good reason.
RAM: Either Corsair or Crucial, whichever is cheaper.
Soundcard: Whatever you have in your old computer, OR a Soundblaster Live!, which shouldn't run you more than $15 or 20.
Videocard - - the biggest and baddest you can afford.
Hard drive - -if you buy RIGHT NOW, Fry's is having a sale on a 400GB SATA drive for $99. you must buy tonight (10/17) if you want it.
Optical drive: Samsung DVD + / - RW with Lightscribe - - $30 shipped from newegg.com
That case supports a 120mm front fan, 2 rear 80mm fans, and comes with 2 side fans. Do yourself a favor and install all the fans the case will support. Overheating is just plain annoying, and modern systems are very good at it unless you manage the cooling well. This will be noisy, but your only other option is water cooling and if your friend isn't keeping current, he may not know how to do that.