I am not sure about the admin rights. I have to check. For now I am the only user and I have installed all the other apps without any problems.
When the MultiShortcutSetup suggested c:/team-mediapo....................... I just replaced the C with a D (where I installed Mediaportal 1.1.1) as the Wiki suggested when using 2 HDD or more.
I have checked my account. I am Administrator for my HTPC