Can only install programs in Safe Mode or from external drive

If I try to run most setup.exe files from Windows Explorer (including Desktop) nothing happens and the Explorer folder (or Desktop) freezes. Doesn't matter if I click normally or as an Administrator, and doesn't matter from which User Account. The behavior is not consistent among all setup.exe files, but most of them fail. I cannot discover any pattern (size, date, name, etc) for which do or don't work, but the ones that do, always do, and the ones that don't, always don't.
The only way that I've been able to consistently install programs is in Safe Mode or from a USB drive.
I've tried disabling all Services and all Startup programs in Normal Mode but it does not help.
Thanks.

1. Scan for malware e.t.c
2. If the problem remains Restore windows to a previus date if exists.
3. Reinstalling windows is the final solution

I solved my problem via System Restore.

McSam said:

I solved my problem via System Restore.

I spoke too soon. Some programs can now install, but not most.