Media Center Crashes on Vista? But Not In Diff. User

I installed Vista Ultimate on my PC recently and got two problems -Windows
Media Player and Media Center would crash as soon as I opened them!

I managed to fix the WMP problem by re-registering some DLLs off the
microsoft site (if that is what the problem was) but Media Center still
crashes - Everytime!
It won't even load the program now! it just comes up with the "MC has
stopped working" and the close program window pops up although for a few days
I could actually get to the set up screen but then it just causes the same
error message and shuts down!

But what is even stranger is that when I created a new user account Media
Center worked perfectly!

Whats going on there? it won't work on my main account but will on another
account!?

If anyone has any solutions to the problem I have had with media center I
would appreciate it. thanks.