I can't open any important windows programs

When I say windows programs, I mean files or programs that come with windows.
Meaning I cannot open many important windows like: the Control panel, Windows photo viewer, Windows live movie maker, My Computer, Volume control, or The Network and Sharing center. When I try to open said programs they open and then they stop working. (Windows explorer has stopped working, Windows is checking for a solution to the problem, etc.)
I've tried searched for solutions and nothing so far has had any positive effect. I've rebooted my computer, done full computer scans for malware and viruses, etc. etc.
Not only are all of the above programs not working, but Steam isn't working either.
My friend tried to tell me that he thinks it's something to do with how I've allocated the memory and ram on my computer, so that might help.

Any help at all would be greatly appreciated,
Thanks.