Computer Graphics Cards Reviews

I'm confused what type of graphics card can my PC?
http://www.pcworld.com/reviews/product/382687/review/et183107.html Sheet # Http://www.aramistech.com/reviews/emachines-et1831-07-review/ http://images.pcworld .com/reviews/graphics/products/uploaded/382687_g3.jpg yes, but then I get DDR2 or DDR3?.
Based on the first link, the team accepts a PCI-E 2.0 (or x16) compatible graphics card.
Sapphire ATI HD 5870 Video Card Review