Memory gets hot

I'm a newbe with a "hot" question, my computer has (2) DDR2 1 gig memory boards after I shut the computer down, and cut the power off at the power supply I noticed one of the memory boards is fairly warm while the other one isn't. My computer has been running slow, and sosmetimes freezes for 30 seconds or more then works, or I have to reset it, so I assume one of them is going bad, but which one? I'm running windows 7 32 bit, the processor is a intel 2.13G core 2 duo. (Forgine my newbeness)