The small black remote is intended to run the Comcast DTA which uses a different IR protocol than the dct700.  You can buy a Comcast DVR remote (red OK/Select button) on eBay for typically $6 shipped.  Use setup code 01376.  You may need to unlock the cable setup code with:
1) Press setup until 2 blinks
2) Enter 982  
The remote should blink 4 times.  If it blinks twice, repeat steps 1 and 2.