Try setting your CMOS to default. Make sure you do not have any USB drives plugged in.
You may need to flash your BIOS. Some part of your hard ware is not working.
That is your MOB telling you there is a problem.
Look up the beep codes for your MOB and see what the problem is.
Black screen? It sounds like your OS has an error. Try resetting your system to an older date.
Could you specify what kind of screen. Photo would be great!
Your hard drive may just be old. Test it and see if you have any problems.