Another easier way is to have compiler folders saved somewhere on hard disk drive and use only symbolic links to switch among different versions (in Windows 2k, XP it works like symbolic links in Unix systems).
For example, in FAR file manager (http://farmanager.com/index.php?l=en) one can create a symbolic link by pressing Alt+F6 and Enter on a folder/file. This link can be used as a resource transparently. An obvious advantage - there is no need to copy/move folders, only small symbolic links.
For the StarCore compiler in most cases it is enough to copy a symbolic link to {Install}\StarCore_Support\compiler folder from another version. However, some GUI libraries are stored in {Install}\bin\plugins\Compiler, so for full functionality it is necessary to replace this folder too.