Vista - Cannot Install a Program

Hi, new here. Needing help with Vista Ultimate, I had installed a realestate program called Agent Office successfully, my client attempted an online upgrade to a new version and it blew up the new/old agent office installation. I did the uninstall from windows of the apps, even used perfect uninstaller and removed all remnants, upon attempting to install started to get the 1607 Install Shield Scripting runtime error, googled and tried numerous fixes. As of now I have UAC Disabled, recreated windows temp, copied the installation to the x86 programs folder and tried to install from there, verified permissions and now when I try to install it I'm getting Invalid Program/System Directory error and still cannot install. Any suggestions appreciated, this is driving me nuts and I am ready to do a factory restore.

You'll probably need to clean out your registry. Download a free copy from Auslogics:
Free Registry Cleaner - Free Registry Repair and Cleanup from Auslogics

You could probably use the registry defragger, too; though not necessary to fix this problem: Defragment and Compact the Registry to Speed Up Your Computer

I thought even MS said not to use registry cleaners.

If you're not comfortable using a cleaner, then don't do it. The issue is controversial but the cleaning actions are not irrecoverable if you know what you're doing.

Will give it a try, thanks.

Nothing corrected my issues, did the F11 after backing up and all is well. When will MS make an os that doesn't need to be reloaded once in a while.