Is there anything I can do to see what happened to it? Is there a chance it came loose? How can I check if it's fried?
edit nobody stole my RAM. I didn't physically do anything to it. I have a Dell Studio Laptop. I'm running 64-bit Windows 7. I don't know exactly what else to specify, I'm not familiar with dealing with RAM.
Update I ran a MemTest but it did nothing except confirm that I had 2 gigs of RAM that worked. I opened the laptop and took out the 2 GB module, putting the 4 gig module in its place. I powered up the laptop, and it reported 4 GB. I then put the 2 gig module in the old 4 gig slot, powered up, and the laptop reported 6 GB. The short story is that I don't know what the problem was, but it's no longer manifesting itself. Don't buy Dell.