I just re-formatted my hard drive and installed all of Windows XP Home updates last weekend and now I'm having trouble installing third party programs such as YAHOO Messenger, Diskeeper, etc. I can download any program but when I'm trying to install any program, it states that setup.exe can't be found and I get a bunch of .DLL errors. One for instance is "Movefile" can't be renamed. I believe something is corrupt in the registry but don't know where to go from there. I tried uninstalling and reinstalling "Windows Installer 3.1" with no success. Why can't I no longer install any programs.

I've scanned my system with Bitdefender, Spybot, Zone Alarm Spyware with no success.

PLEASE HELP and thanks