They only have one version.
We must protect them from themselves.
Mr. (Randy) CADaver may have some experience in this regard, lol.
We control everything from the network and from local desktop icons with client/contract specific setups. A user clicks on a client/contract icon and he's loaded the proper version with the proper settings and profile.
The users are free to use whatever they wish as long as the results are the same, but there's the rub. If they use company stuff and it blows up, it's my fault, I'll take the heat. But if a user ignores our shortcuts in favor of his own methods, he'll take the heat (considerable heat) for any blow up. We try to make it easier (less painful) to comply, than not.
The only drawback I have to our current system is that we limit one session of ACAD at a time. If I'm running an R2002 project, and need to review something on an R2005 contract or another R2002 project, I have to exit the current R2002 session first.
I've solved it by adding another network link in my office and firing up my laptop when I need the additional session. I've had a couple of strange looks (not all that rare at all) when they see my laptop propped up on the destop's keyboard, and me running two mice (mice? mouses? meece? mooses??)
Note that I don't mean Randy in the British way.
Even if you did, it'd be one of the nicer things I've been called around here