After searching for answers with no success, I finally accepted that I was either going to fix the problem or reinstall Windows from scratch. Guess what? I'm back in action without the reinstall. Hope the following helps someone: Problem: Windows Installer not working but everything else seems OK. Cannot update Windows Installer. Cannot reinstall Windows Installer. Cannot install anything that requires Windows Installer. Discovery: Windows Installer executable (msiexec.exe) is 0 bytes. The only account with access to Windows\System32 folder is "TrustedInstaller". Unable to find any malware with any tool I could install. Solution: This is heavily abridged, but ultimately all I did was... Take ownership of Windows\System32 folder to Administrators. Paste a good copy of msiexec.exe into the folder. Everything started working immediately. Hopefully an MVP will point me to the solution I should have found, and tell the Windows team that a new FixIt solution is required. --Brian

Please post your query in the related forum as this forum is dedicated for Server technologies http://social.technet.microsoft.com/Forums/en-US/category/windowsvistaitpro http://social.technet.microsoft.com/Forums/en-US/itprovistaapps/threads http://www.virmansec.com/blogs/skhairuddin