I recently built a new computer with 4Gb of ram, was all working fine, but just the other day I noticed that in now says it has 4GB of ram installed but only 2GB useable.
I check the ram sticks individually and both work, I checked the bios and its states total memory is only 2GB.
Specs of machine:
RAM: G.Skill 4 GB
OS: windows 7 pro 64bit