Shoutbox

When installing I get this Dutch error:
I will translate it in English:

Messenger plus! Installing data error!
Access to disk has been refused or installinf file has been damaged
Some possibilities to fix the problem are:
Login with administrate rights(I'm the only user)
Install in another directory(I thought it was installed in program files and where else it has to be installed)
Restart computer(already done)
Download from another source(where??????)

After that msn messenger is opened without msnplus functions and when looking for msnplus in the programfiles folder it seems to be installed(but maybe it is not complete)