I have a Dell c840 and yesterday a student put a password on the computer while I was gone. Now when i turn it on the grey and white screen administrator password protection screen comes up. I have looked at some of the other threads to see if there solutions will work for me. I have tried the DST CD ISO Cd but it will not boot from The Cd apparently. I put in it in the drive and hit f12 and the screen still comes up. Is there any thing I can do to get rid of this.