I don't know if there's a registry key but this does it for me.
1. Register it manually.
2. Take the following files from C:\Documents and Settings\All Users\Application Data\Apple Computer\QuickTime
- com.apple.QuickTime.plist
- QuickTime.qtp
3. Copy those files back into that folder after you've installed quicktime.
I just create an SFX archive and use this comments on winrar
CODE
Path=%ALLUSERSPROFILE%\Application Data\Apple Computer\QuickTime
SavePath
Silent=1
Overwrite=2
it's posted somewhere in the forums lol