System was working fine with GUI interface for a couple years. Then one day i found that when i login to sys. it just has a black screen. I can get to task mgr. via cntrl/alt/del and do most anything i want, however no matter what i have tried, and it has been many things, can't seem to get the gui to come back, Please Advise, with a old clone of sys. it works fine, verifying that all hardware is fine...