I was working on my computer when the monitor suddenly went black. Nothing seemed to be different in the tower; there were no sound changes, no light changes. The monitor's power light stayed on. I recently acquired another computer and monitor from a friend and decided to hook both monitors to both towers to troubleshoot. Both monitors work fine when hooked up to the second computer, and both monitors stay blank when connected to the first computer. So, the problem has to be in the tower. What sort of problem does it sound like I have? What should my next step be? The only spec I have for the machine, since I can't access the hard drive, is that it's running XP.