I was upgrading the ram on my sisters Macbook Pro late 2011 from 4 GB to 8 GB. After the replacement, I turned it on and everything seemed to working. Later, I got a call from my sister and she told me the Mac wouldn't turn. She got the Apple logo with the loading circle beneath. Tried putting in the old ram again, but had the same problem. After some troubleshooting, I discovered there was a problem with the hard drive (I don't remember the exact problem now). I had another hard drive from my Mac, so I put that one in and installed OS X 10.6 (the only one I had on DVD). The computer booted up fine, so I decided put in the new ram again. When I started it up now, I got a black screen and three beeps. After a google search, I learned that it was either a problem with the ram itself or the ram slots. Both ram sticks work fine in the lower slot, but when I try to put in the upper slot, I get the 3 beeps again. So most likely there is a problem with the upper ram slot. I tried to do a search for any solutions, but it appears that the logic board needs to be replaced. Since the lower slot is working fine, I could just buy a single 8 GB stick to use there, but I'm curious if there are any other steps I could take to make it work again? I tried blowing the slot with compressed air.