Windows XP: MS Installer Problem

MS Installer Problem

When ever I try to open a folder on my desktop, MS InstallShield comes up. I checked out the event log and it says this.

Detection of product '{33E27482-5682-44EB-81CE-DBE07461A888}', feature 'Core' failed during request for component '{436D7A23-36BE-11D2-ACBB-0080C7FCBB84}'

Usually closing explorer.exe and re-opening will unfreaze my system, but it still brings up installer. My anti-virus (avast!) and some other programs, like the Services manager bring it up, too, and cause them to freaze.

I'm running XP SP3, 2.66ghz P4, 510Mb of ram. There was a program that got stuck while isntalling, but I removed that from the installer cache with the Windows Installer Cleaning tool, but I'm kind of tentative about removing EVERYTHING. It says that i may have to reinstall some programs if I remove the Install Sheild information with the cleaner tool.

I'm managing to get around with Task Manager and Run, but it is really annoying and I'm getting sort of tired of it. . So ANY help would be great, and if anyone else is having this problem, just post a reply and maybe we can get this thing fixed!!!