So basically this is a weird problem I've encountered and believe it has something to do with windows 7 openGL support.
Versions of Hammer 3.5 and below one day started crashing on splash screen and I haven't been able to open them since, this happened the same day Counter-Strike 1.6 started crashing very frequently on game entry.
I have uninstalled all versions of hammer multiple times which hasn't helped at all either.
So basically just praying that someone has had a similar experience and knows a fix because I don't really want to have to reformat.