.dll file

[Pat B]

In a fit of stupidity, I associated my Windows XP.dll
files with a third party utility program. Now, whenever I
click any .exe file, I launch not that file but the TPUP
(third party utility program.) When the computer re-boots,
it launches 19 copies of the TPUP, reflecting, I guess all
of the programs and applets in the start process. This has
also had a strange effect on my user status(I am the only
user and, thus, the administrator). It seems that I can
work around the launch problem by right-clicking an .exe
as selecting :"Run As", then unchecking the box that
says "Protect my Computer and Data" Pressing OK launches
the Application. Why this works is a mystery. System
Restore will not work because when it goes to reboot, it
launches the damn TPUP-not whatever restore files it
needs. I have tried Folder Options to change the
association but the dll extension does not appear on the
list of files. I have never edited the Registry, but would
be happy to try anything to avoid a reinstall of XP. I
also have a clean backup copy of my previous Registry
(before the problem). Any solutions?