QUOTE (vfnaomi @ 3-16-08, 4:43am)

did you check crucial.com
Although Crucial will tell you what type of memory is needed for a particular make/model of computer, Crucial sells their own brand. Crucial.com will not tell you if HP PX976AT is compatable with a Dell computer as they don't sell HP branded parts.
The Dell 531 uses DDR2-667, but the only real way to know if the stick will work is to install it.