A problem caused the program to stop working correctly windows

Hello all, I'm kinda new to this so please bear with me on how to do things like this. I want to start off first by saying THANK YOU for helping out, even if you're in the same boat like me and can't figure it out. at least you did take the time to read this.

The very basics are :
I'm running Windows Vista Ultimate on a Dell PC that I got for Christmas in 2008 or 2009. I AM NOT very good with the whole Internet thing nor do I know allot about computers. I'm not sure if it was something that I installed or downloaded or something that one of the other people here did.

The problem is that EVERY PROGRAM that I try to run (that is new), will not work. It crashes and give me a text of :

A problem caused the program to stop working correctly. Windows will close the program and notify you if a solution is available.

I have TRIED to download and install :
Trend Micro HouseCall
RootKitBuster
cbsidlm-tr1_8-Free_Window_Registry_Repair
WinZipRegistryOptimizer
ARO2012_uc
HijackThis
and a few more, and ALL OF THEM I get the same thing.

It seems like it wants to install them but it stops right towards the end on most, and on others it will seem to be done, but nothing comes up after, and THEN I get the "A problem caused" screen.

I would prefer NOT do do an entire reinstall of the OS because there is just to many programs I have installed that I don't know where the original disc's are.

I really do not know what to do. I can not afford to call a Best Buy Tech out here nor can I afford to bring it to the store. I have the OEM DVD that came with it, but can not figure out how to "FIX" the registry if that is even the problem. I've read ALLOT and am still unsure of what the actual problem is. I'm thinking it's either a virus, or a registry problem, or somethign else I just don't know anything about ?

Any Ideas on what I should do.
Any ideas on where I should start ?

Thanks For reading this,


Dan


-EDIT-
So I know it's only been "overnight" and I've still tried other things as well. As it is now, I can't even get windows updates AND I can't run Windows Defender. I get the same problem of a different sort. It tells me that the program can not start and for me to reboot and try it again. (Of course that is not the EXACT text, but something along those lines?