I might have a solution for you.  Sometimes when we uninstall software on a Windows Machine there are components and pointers in whats called the regsitry that stick and point to files that are no longer there and cause issues.

One of the tools I use in my arsenal is CCLeaner

http://www.piriform.com/ccleaner

Download the free version and Run the Registry cleaner it will on the left side of the program under its own tab.

 

It will ask you if you would like to do a backup of the registry changes before fixing the problems.  Say Yes and save the file somewhere incase something goes wrong.

Scan for errors a couple of times, till you no longer see any errors.

Then try to reinstall 7 and let us know if this trick worked.