How to set my program as the default opener

I need to make a new file type and then set my program to the default opener for that file type. I did this before, but I lost the script. Basically, it involves makeing a key in HKCR named .ext, then make a shell key and then the open action. I think MS changed how Windows makes it's actions in the registry - since it doesn't seem to use shell anymore, even though shell still works... kind of =/

WriteRegStr HKCR ".abc" "" "abc.Name"
WriteRegStr HKCR "abc.Name" "" "abc.Name"
WriteRegStr HKCR "abc.Settings\DefaultIcon" "" "$EXEDIR\abc.exe,1"
WriteRegStr HKCR "abc.Name\shell" "" "open"
WriteRegStr HKCR "abc.Name\shell\open\command" "" '"$EXEDIR\abc.exe" "%1"'

Or with some greater detail: