Function keys not working.

I've a dell Inspiron 6400, it was working fine since last night i found that i'm unable to use function keys Fn+F2, Fn+Up arrow/Down arrow. I tried pressing MediaDirect button near power button but it said to install media direct software on machine. After repeated attempts to install MediaDirect from CDs provided by Dell,  i couldn't fix it. I tried using disgnostics by tapping F12 on booting.

I encountered error code 0148, message error code 2000-0148, Message unit 2: IDE error: status 29 No additional sense information.

What is the meaning of this error and what should i do to fix it. Rest of the things are perfect with my machine except using Function keys. Please suggest.