Acrobat Reader 5.1 reinstalls with every use

Going slightly batty with an Adobe Acrobat Reader 5.1 prob.

Have many WinXP Pro workstations and have noticed on a few
of them (but not all) that every time a user opens a .pdf
Acrobat reinstalls for every file they view. Acrobat has
been installed from a .msi file which we created and are
using for remote administration purposes. The reinstall
definitely crops up for users w/ "Domain User" rights, but
doesn't seem to affect those with "Power User" or
"Administrator" rights. Making all users "Power Users" is
not a viable solution.

I've tried uninstalling Acrobat (w/ Add/Remove Programs
and manually), reinstalling from the .msi file (as an
Administrator). Interestingly, when I uninstall using
Add/Remove Programs, Acrobat Reader reappears almost
instantly - it doesn't actually go away. When I'm logged
in as Administrator Acrobat Reader stays installed, no
problems. I've tried installing the Reader with as the
User w/ Admin rights - but as soon as I "demote" the user
to regular user status the problem reappears.

So, why won't the Acrobat Reader install "stick" for a
Domain User?

Thoughts, Ideas, Suggestions?
Tim