Can't install program with admin. account

[Les]

Just recently I started encountering a strange
problem...I'm unable to install software on my system.
Under my user account "Les" which has admin. privileges,
I couldn't install a new program. The error message said
I need to contact my administrator. I then logged in as
the administrator but I got the same message. I assume
this is a problem with my registry? How can I fix it?
Thanks in advance- Les