Windows 7 64-bit when I first installed it showed only 3GB of ram. I thought it was a mistake since I had 4GB so I got CPU-Z and restarted it and it showed 4GB of ram. I restarted it and it showed 4GB of ram and I thought it was all fine and the 3GB of ram happens from time to time but now when I checked my RAM it showed 3GB so I went into CPU-Z and it said around 3GB so I tried BIOS and it said around 3GB. Could this be faulty ram?
It is your motherboard most likely. You need to enable PAE (Physical Address Extension) to get the motherboard to recognize anything over 3GB of memory. 32bit OSes recognizes only the first 3GB of memory. Consequently, most of the MoBo's do not have PAE enabled by default even if you plan on using a 64bit OS.
I had this same problem. I checked around and it was suggested to enable memory holes in the bios, then the full amount of memory showed up. I did not research why this worked, but I can only say it did.
Never mind people! You can close this thread now. It was caused by a faulty piece of RAM and when I tried to remove it and put it back in I was stuck at the boot-up menu so I tried removing various sticks of ram and picked one out and started the computer up and now it is good.