The most likely cause: a virus. Try the patch you can download (on another machine) from http://www.annoyances.org/exec/show/article07-102. Copy it to diskette, and click on it (if you can get into My Computer, or type a: in the Start>Run box).
Hope this helps.
A computer running Windows 98, previously worked fine, suddenly stopped working after I gave it to one of the kids. It boots up normally, and the desktop looks normal, but I am unable to open the control panel or any programs. I can look at the list of programs in the start menu, use the mouse to look at properties, etc, but that's it.
My stepdaughter tried go online with AOL and had a problem. She then tried Net Zero and had the same problem. (This computer was not previously used on the internet, I believe it may have been used on an office network, I got it for my mother to play games on). When she gave it back to me to try to find out why (I was going to buy an external modem and try to subscribe to a dialup ISP for her) the word processing, games, nothing worked anymore.