Windows 98 wont load

well thats not entirly true, Win98 starts up (i get the blue screen with the Windows logo and Windows 98 under it) but then it comes up with the Windows 98 Startup Wizard and asks for my name and CD-Key.

Why is this suddenly coming up, I was using the computer, it was running slow so i restarted it and now i get what i said above.

If i enter the CD-Key and im guessing it will try and install Windows, will i lose everything on the Hard-Drive? And is there any way around this.

Many Thanks

Lee Daniels