That sounds entirely too simple.
I think I have tried that, but I was so much younger then. In fact I did rename c:\moodle\mysql\moodle to moodle15 and changed the config.php pointer. I think I got into trouble when I tried to rename c:\moodle\moodle to c:\moodle\moodle15. I will go back and check.I have made progress:
Before I had a seperate Windows XP computer for each server that controls one version of moodle. I now have 1 computer, with 2 different servers, each directing a different version of Moodle. Creative copying of a directory and a quick edit on c:\moodle15\apache\config\httpd.conf and c:\moodle15\moodle\config.php, with a 127.0.0.15 IP and a moodle cookie of MoodleXV worked. Then it was child's play to install 1.6 in the old c:\moodle. Since I was on a roll, I renamed that directory to c:\moodle16 and the did the edits on the two files and the cookie. Yes I have to start and stop each Xampp before the other will work, but that actually keeps me out of trouble.
For those who stumbled here and want a longer non tech version of what I did on my XP standalone computer at home : http://docs.moodle.org/en/Windows_1_computer_many_servers
It is dumb (techies please note), very specific to my machine, and does not rely upon renaming MySQL databases.
And thanks to everyone for their assistance. I am still figuring out how to install PHPadmin, but I got MySQL admin working. The whole process has been very educational for me. Right now nothing is broke and I am happy !!!!
