Bad Serial Error as Limited User (Windows XP)

[Sebastian]

I'm using Windows XP SP3, MixVibes DVS 7 (7.21, but I've got the same problem with 7.1) and when I log on to Windows as limited user, I get the error: bad serial

(that's German)
It works fine when logged on as administrator
And please don't come up with something like log on as administrator or use start as administrator.

[UncleVibes]

If you log as a visitor then you arrive to an another part of your computer. Different my documents, different desk and different place to get instructions. You should install mixvibes in this place as itsn't now. (sense of the error message)