If you are getting garbage Ether, then you do have some problems with memory, either Video ram or actual ram. Whether that corruption is due to an actual physical problem or a software problem you will have to do some reinstalls to find out. I would reinstall the vid drivers first and formost, defrag the HDD (For the virt mem) and depending on the OS, maybe have to do a clean re-install of that. Corrupt files can cause the garbage. Also, overheating of the vid or main processor can do it too. I had to add a small fan from Radio Shack (DC, 5v I jumpered it into one of the power cables) to the heat-sink on my video card because I was having the overheat problem (I have a cheap card without the built in fan, obviously ;) )