|Go to the link and download the exe file association fix and follow the Usage Instructions.|
File association fixes for Windows Vista
Note: If you can't access the Internet with the problem computer use another computer to download the reg file fix onto a CD, thumb drive, or floppy and transfer the file to the problem computer.
After that .reg file is merged into the registry successfully restart your computer
Edited to add: As far as running malware bytes go into your C:\Program Files\Malwarebytes' Anti-Malware folder and rename mbam.exe file to something else like eradicate.exe then try to run the malwarebytes program.