Not sure what you have tried but here is how I do it.
1 open the program
2. click on the little film real in the upper right
3 click on the mall yellow folder in the upper left
4 Select your external drive and select avdata
5. select the date you want in the calendar
6 drag a box around the time and camera you want
7 slide the process bar left or right till you find the exact start time you want and Click the cue int (lower left)
8 Do the same the for the cue out.
9 click on the same to AVI (top right of the six icons on right)
10 enter file name and OK to same file
Hope this helps