add/remove programs doesn't work

I'm Running windows 2000 Service Pack 4
when I go to Add/Remove Programs it gives me this error
"An unexpected error occured.

Class not registered

res://appwiz.cpl/listbox.htc
line 225"

I click ok, where the programs are listed it says there are no programs installed on this computer. but I scroll down and it list them ass normal (there's just a big blank spot at the top of the list). I select an program and the change remove button are greyed out. any ideas? I'm not terribly technical so try to make the answers easy to follow. I live in a dorm and asked one computer science major and he had no idea. please help. oh btw I have run antivirus, ad-aware and spybot.

 

Try this. May have to restart, not sure.

1. Click Start, click Run, and then type CMD.

2. At the prompt, type REGSVR32 APPWIZ.CPL

Steve

 

That didn't work, it said "DllRegisterServer in APPWIZ.CPL succeded." but there's no change in Add/remove Programs

 

Go here, http://support.microsoft.com/default.aspx?scid=KB;EN-US;266668

Steve