Perhaps the Registry association has been altered. If you
right click on a .dll or .exe and select properties, does
it have an "opens with" associated with it? What kind of
icon represents your .dll and .exe files? If it is a
Windows icon, Windows may not know how to open. If you
double-click on an .exe file, does it respond with
a "Windows does not know how to open this file" ...choose
program? If so, you must choose the correct program
association. Uncheck the "Remember..." box and try it.
When you choose the correct program and it opens
successfully, you can do it again with the box checked to
make it do ti every time.