Boot up stops at a black screen with a blinking cursor.

I have a Dell Dimension 1100 just over a year old. When I start it up it goes through the Dell screen and then stops at a black screen with a blinking curor.

 

I can't go to Setup or Boot Menu.

 

Last thing I did yesterday was run CCleaner (recommended by PC World). It appears to have deleted something Windows XP SP2 needed.

 

Tried to boot to the reinstallation CD but same result. HELP!