Your PocketMate (TM) DVR with Date and Time Stamp saves ASF files onto the
SD card.  I have found that about half of the saved files are unplayable by
all players.  However, these files can be fixed.

Download the AVI/MPEG/RM/WMV Splitter from here:

http://www.boilsoft.com/download.html

Open an ASF file that doesn't play, set the begin time to 00:00:00, the end
time to the duration of the clip (which is displayed), the resulting ASF
clip will work fine.