My friend recently ordered parts for his pc, and did absoulutly no research before purchasing the parts.(aside from reading the reviews on the site) the specs are

Asus p5k-E LGA 775 Intel P35 ATX Intel Motherboard

Intel Core 2 Quad Q6600 Kentsfield 2.4GHz Lga 775 Quad-Core Processor

G.Skill 4GB 240-Pin DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory

Seagate Hard drive, and a SAPPHIRE 100243l Radeon HD 4870 512MB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready Crossfire Supported.

He just ordered all the parts off newegg on a whim, and I don't know much about pc's to see anything wrong with it. Is any of this going to be a problem for him, and if there is a problem what else should I tell him to order (or send back.)

So any videocard will be compatible? It's not a slim cased one, but not huge. If thats all I need then great! And thanks for all the help guys, I know most of the questions I asked were common knowledge to most here, so thanks again.

Just to throw this out there, the pc that im posting from is brand new hp, with a 8500gt. I really don't know if that means anything, and don't know level progressions with pc's, but could that be upgraded and still run games?