You say you did a disc clean up. What did that consist of ?
Did you run a cleanup program and if so which one ?
Or did you just delete some programs or files yourself ?
It sounds as though some important files needed for Windows have been deleted (the Kernal is a key part of Windows).
If you have the Windows CD you could try a re-install over the top of the existing windows.
If you dont have a Windows CD and have a recorvery CD you may need to do a complete recovery of Windows, but you may lose any files you have on the laptop.