By default MS-DVR files are not editable through Windows Movie Maker 2.1. A little tweak that has been around for several years just caught my attention. I don’t know the original source, however, know that I am not.

Import the following into the registry and reboot.

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\CLSID\{083863F1-70DE-11d0-BD40-00A0C911CE86}\Instance\{A4F9C3BA-A68F-4942-8152-B783CF89193F}]
"CLSID"="{A4F9C3BA-A68F-4942-8152-B783CF89193F}"
"FilterData"=hex:02,00,00,00,00,00,20,00,04,00,00,00,00,00,00,00,30,70,69,33,\
00,00,00,00,00,00,00,00,01,00,00,00,00,00,00,00,00,00,00,00,30,74,79,33,00,\
00,00,00,b0,00,00,00,c0,00,00,00,31,70,69,33,00,00,00,00,00,00,00,00,01,00,\
00,00,00,00,00,00,00,00,00,00,30,74,79,33,00,00,00,00,d0,00,00,00,c0,00,00,\
00,32,70,69,33,08,00,00,00,00,00,00,00,01,00,00,00,00,00,00,00,00,00,00,00,\
30,74,79,33,00,00,00,00,b0,00,00,00,c0,00,00,00,33,70,69,33,08,00,00,00,00,\
00,00,00,01,00,00,00,00,00,00,00,00,00,00,00,30,74,79,33,00,00,00,00,d0,00,\
00,00,c0,00,00,00,76,69,64,73,00,00,10,00,80,00,00,aa,00,38,9b,71,00,00,00,\
00,00,00,00,00,00,00,00,00,00,00,00,00,61,75,64,73,00,00,10,00,80,00,00,aa,\
00,38,9b,71
"FriendlyName"="WMT MSDVR 2 Dexter Filter"
@=""

[HKEY_CLASSES_ROOT\CLSID\{A4F9C3BA-A68F-4942-8152-B783CF89193F}]
@="MSDVR"

[HKEY_CLASSES_ROOT\CLSID\{A4F9C3BA-A68F-4942-8152-B783CF89193F}\InprocServer32]
"ThreadingModel"="Both"
@="C:\\Program Files\\Movie Maker\\wmm2dvr.dll"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MM20\MSDVR]
"MSDVRMinimumVersion"=hex:43,21,00,26,05,00,05,00
@=""