in reply to Win7 - multiple Perl distributions?
Also, watch for library version conflicts: many Perl modules rely very heavily upon system or application libraries to work their magic, and you need to be extremely careful, not only that they properly identify and recognize the libraries upon which they depend, but that installations and re-installations performed in one Perl-version context do not de-stabilize another. Windows is very dependent upon its global Registry.
One pragmatic suggestion I'd make is that you should set up an entirely-different, non-Administrator, user account under which to perform, say, your Strawberry testing. Make sure that the installers do not request, and do not receive, Administrator-level access. If this is the case, then any registry keys should be under HKEY_LOCAL_USER; hence, better-isolated.