Add/Remove Programs applet opens Notepad

I have a W2K pc with sp4 and am unable to open Add/Remove Programs. Double-clicking on the icon opens Notepad and gives error “The filename, directory name, or volume label syntax is incorrect.” All other Control Panel applets work fine. Running Appwiz.cpl from the Run line produces the same result. Appwiz.cpl has been replaced. Spybot and Pest Patrol have updated and run. Appwiz.cpl, mshtml.dll, and oledb32.dll have all been unregistered and reregistered. Any further ideas?