Windows Update Error 1601 when trying to update Comodo Antivirus

I am trying to install Comodo Antivirus but a box told me that I can't install it to my system due to
Windows Installer is not accessible
Installation can't continue because the Windows Installer could not be accessed
Error code: 1601
I opened the Task Manager Window and checked if there is another installation process running. To make sure, I end the process of each .exe that is familiar to me. But I still cannot continue. How can I know if my Windows installer is corrupted? Can I completely remove it from my computer?
I already downloaded Windows Installer 4.5 Redistributable. My current version is Windows Installer 3.1. I tried to boot into safe mode, but that didn't solve the issue. I am under Windows Vista Home Premium. I also found out that this error does not only occur upon installing my Comodo. But also when I am trying to remove or install any applications. The install and remove will stop and indicate the same error message.
I searched on Google and found something that will resolve the issue. It is about using the Windows Installer Cleanup Utility to remove false configuration.
Where can I find this cleanup utility? I am lost. Can someone please help me?
