loss file association

Somehow, my system lost file association for exe files. Could not run most application, nor could I run "Restore". It was OK right after install. Not sure how I got to this point.
There were 3 areas after install that did not have the right drivers. I was trying to correct when I noticed the system went west. These were: the AMD processor had an "!" next to it with the comment driver not loaded, trying to re-load did not help, The printer did not install, Lexmark 7170, and the driver for my monitor, Samsung 930b did not load - it went to default.
I had to re-load Vista and all three were OK, no problem with File Assocuiation.
If it was something I did to reset the file association, it was blank for "exe" I do not know what I did, but it would seem that this is so basic that there should be some protection. I did try to set the file association to "basic dll" but this was only a partial help.
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