I'm trying to use this to backup some old keys before installing an application (it is one of those which steals extensions). I use Windows 7 x64 Pro, TCC with "Run as Administrator". However, for some reason the command: %@REGCOPYKEY[HKCR\.mp4,\oldkeys] returns 0 (not copied). All variations (quotes,not quoted, etc) of the parameters seem to do the same. .mp4 and oldkeys are existing keys (the latter is empty). However, if I use %@REGCOPYKEY[HKCR\.mp4,HKCR\oldkeys] it performs the copy, with one issue. They end up in HKEY_CLASSES_ROOT\HKCR\oldkeys The question is, is this a bug? i.e requiring HKCR,HKCU etc to be specified in the second argument for the copy to succeed, but failing to remove it from the keyname (the docs says source and target must be in the same root)?