My son has a small Optiplex SX270 lunchbox style computer that I can't boot up. I can get into F12 and F2, but I can't get into safe mode. It will not boot from a CD. When it starts up, it appears to start loading the OS (Windows XP), but after a couple seconds the screen goes black and I see nothing except a blinking cursor in the upper left corner. There are no POST beeps. The only selection I can choose from F12 is number 5 (IDE drive diagnostics). It runs and tells me that the hard drive passes. Any ideas on what I can do to make this computer boot up?