can you give more details?
laptop or desktop?
how old is it?
windows? XP, vista, win 7?
or mac?

You might check all cables & cords plugged into the computer, maybe someting is loose or has a bad wire??

could it be saying the hard drive is nearly full?

We really need more info to give better help suggestions..
but if it isn't starting up fully - it could be a hardware failure , a virus or some sort of operating system failure.

Those are pretty hard to diagnose witout being there in person.
Do you have a friend or neighbor that is handy w/computers?

If you have an installation cd you might be able to do a re install but that would wipe out all files and information that you now have.