How do you unrecord programs on dvr?

Depends on the make of DVR. The handbook is the best point of reference.

Usually if it is in the process of recording, simply pressing the 'Stop' button will do it.

If it is a program to be recorded, go to the 'library' or 'list' menu, select the program and either press 'record' again or one of the coloured buttons (depending on make of unit).