I created an installer, and I wanted to give the users the option to have a command under their rightclick button to process the file click, just as "Compile NSI"

I put these regstring in the installer, but they only work on my pc and not on other pc's.
Can anybody tell me what is wrong?
=================Code=================
WriteRegStr HKEY_CLASSES_ROOT "AVIFile\shell\PackDivX" "" "Pack DivX"
WriteRegStr HKEY_CLASSES_ROOT "AVIFile\shell\PackDivX\command" "" '"$INSTDIR\PackDivX.exe" "%L"'
=================Code=================
The option should only be available when clicking on a file with the AVI extention.

Thanks