Update Interaction between X programs

Many of us have kept old versions on our systems unless we had to do either a new computer build or OS.  This goes back to Pro Audio days and no one has reported a problem. 

Danny yes it makes sense but that doesn't mean much. I was trying to point out that I for one had four different versions on my Vista setup with X1 and didn't have any of the problems some others had. Right now I don't have any version other then X3 c Producer on my system and can report one crash that I believe is due to opening an old file that was created in X1. It crashed with X2 and now it will crash in X3 if I do the same things with it. 
 
What CW does with its dlls and plugins is upgrade those but that wont interfere with old versions. How many times have you for example gone back and opened a project in an older version and had not problem? I have on occasion and can report no issue as long as the project is compatible with the old version. That is I haven't saved it in the new version and made it incompatible. The point is that often plugins and some dlls maybe new but don't stop one from opening or accessing that project in an older version. 
 
We know that the linear phase 64 EQ was reworked and it works in the older versions. 
 
However as an idea its not a bad one but as I implied in my post above it would seem that it would have been mentioned by now if it were known to cause problems.
 
Don't forget that most if not all of the critical files associated with a given version are placed into their own folders. Only those files that by their very nature are benign are in fact shared.
 
A plugin shouldn't cause any problem even if its been updated for a newer version for example.