Problem with IE on Vista computer

I'm stuck and I'm hoping someone can help me here. This afternoon I was given a Dell desktop with Vista to fix. This person claims they uninstalled IE and instead installed FireFox. I thought ok simple fix I'll go into the computer uninstall FireFox and re-install Internet Explorer. I went to do that and successfully uninstalled FireFox. I then started to install IE 9 from my thumb drive but I get an error say "Internet Explorer did not finish installing Setup can not continue because a more recent version of IE is already installed on your computer." I then went to Add/remove programs to delete IE because I figured something got messed up but IE is not listed in programs. It is however still listed on the start menu and when I click it it doesn't launch it just instantly pops up saying IE has stopped working. I really don't know what to do. It's as if it is there but not there.
 
I would install something like ccleaner (click on advanced if you install it, to opt out of installing Chrome)

And see what toolbars etc have been installed. Something like this maybe making IE freeze. Go to tools/startup / IE tab / browser tab

Or look in programs and features whatever it is for malware / adware..

If theres anything there uninstall it

Then use something like adwcleaner (http://www.bleepingcomputer.com/download/adwcleaner/), to scan for the remains (if there's adware/malware on the system

 
Tried re-installing 32bit IE and I got another error saying it is not valid. Even though it is not showing up in programs IE is obviously still on the computer . Any way to force uninstall it or delete anything related to it from the registry?
 
Well it turns out that it seems a virus or viruses were causing all the problems. Running Avast and Malwarebytes they came up with a bunch of Malware and viruses. After getting rid of the viruses IE explorer worked fine. I didn't even need to re-install Explorer.