Running PSP 5 on a limited rights account?

Hi,
I'm trying to run my old PSP 5 on my new computer with Win XP SP2.It works 
fine on an user account with full administrator rights, but when I try to 
run it on a limited rights account (which I use for surfing the net, etc.), 
an anoying error message pops up every time I start Psp:

"Failed to update the system registry. Please try using regedit."

Otherwise, the program works fine.

The Problem is that it doesn't tell me what to change with regedit...

Any ideas? Thanks in advance.
Felix