Guess account error in Media Center! HELP!

I love using Windows Media Center...

or else... I loved using it, before it stopped working a few weeks after I
installed Vista. And now I am tired of putting up with it.

Other then the embedded administrator account, (which I have enabled since
then and opens media center just fine), there is only one other account on my
PC (my account) which is in the admin group.

It is not a guest account, to clear things up. However, when I try to open
Media Center, I get a message that says "You are currently logged in as
guest. Windows Media Center must be opened from a non-guest account."

Problem is, I am not a guest account XD

I have tried EVERYTHING to fix this issue. There are a few others crying for
help across the net, but no one has a solution.

I want to install a TV tuner and I need MC to work! Has anyone else had this
problem, or better yet, does anyone have the remedy to this issue? I'm about
to pull my hair out