This is one that techs won't be able to solve because it could be *anything*.
However disk formatting and mouse and keyboard are at the bottom of the list. The next thing to try is
memtest. Download a bootable CD from their precompiled bootable ISOs. Use the ZIP version. Decompress it and use your CD burning tool to write the raw ISO image to disk. Your CD burning tool will have an option to "burn raw image", this is what an ISO is.
Once you've done that, you'll have a bootable CD that will boot and run memtest by itself, without Windows getting in the way. It tests your memory. By itself it will run test after test until you stop it. One good idea is to let it run overnight. Hit us back with questions or problems.