Windows Media Center have replace my system and .exe files

Hi!
Have W7 Professional 32 bit Service Pack 1, Intel Core 2 Duo CPU, 1.00 GB. My problem is that Windows Media Center have replace all my programs, icons and .exe files. Can´t use the Notebook! It is not a new one (HP 6910p) but it was working very good with W7. I have been trying to do the basics things to fix but without Panda and Internet is not so much I can do. Just now I am writing this in a friends computer!
Somebody who kan explain what to do and in a simple way?

Hello Kronet,

What were you doing just before the issue started?

Did you download anything?

John

Hi john s, nice that you answer. I was looking to the W Media Center program but it was not activate so I let this because I didn´t have enough time that day. Later when i tried to use the computer, I saw that all the icons in the desktop where changed to the Windows Media Center.