Finally fixed my problem, having been scanning, downloading and what-not virtually all day. I eventually stumbled across a forum that explained what my problem could be, and solutions to fix it. It turns out that some of the registry paths were deleted because I have recently added another antivirus program to my computer, and sometimes they are unable to run side by side. The solution that I used was the 'doug knox fix' and it was so simple to do. Took me 30 seconds to fix a problem that I've spent the best part of 6 hours trying to solve!
Cheers for the help though Mike, and if anyone ever has a problem opening .exe files then take a look at the following help page
I can't open EXE files - Tech Support Forum
never have 2 AV programs installed at the same time as it can cause problems for your PC (as you can see). If you want to change AV program, uninstall your current one and then install your new 1