Double clicking to open а default lister doesn't work on Win7!
Yes it does!
if i use deskscapes from stardock Dopus double click must work? 
don't know must it?? 
It won't work if you've replaced the Windows shell or desktop. If you're using a non-standard shell and/or desktop then it's up to you and/or that tool to change what it does when you double-click on parts of it.
It's just another window on the screen as far as Opus is concerned.
As this is the pantomime season, shouldn't' that be "Oh yes it does!"?
LOL! If this is the pantomime season, who's playing the Pamela Anderson part?
I'll play with Pamela Anderson's parts...
...oops sorry, I misread that 