Help w/ Inpiron 1520 -- Dell Media Direct

I have  a Inspiron 1520 -- My 7 year old pushed the "house" btton on the top of the keyboard close to the power button and DELL MEDIA DIRECT came up - I can't get rid of it and go back to working with regular old XP -- In fact it does not even load properly --- it givem me a screen that tells me that Media Direct could not access my Hard Disk as it may be encryoted ???? I have the option to exit but then it simply shuts down the computer,  When we go to power up the same loops starts over again ... etc.

HELP>>>>>>>> HELP, pleaase