That could mean your HD's toast. Does it make weird sounds when you turn it on? If it doesn't, then some of your boot files are damaged, which can be fixed with the Windows CD (which you don't have atm).
My buddy's computer said that and he had to get a new hard drive and reinstall Windows. But his was making clicking sounds. This means he lost all his documents, pictures, etc.
But if this had happened before and went away by itself... then it could be a bad motherboard.








