You can also access the site via different servernames from the same browser. Since the cookies are distinguished by servername you will get a different session by requesting www.yourserver.com and yourserver.com, or the ip-address. Or add different aliases in /etc/hosts on the machine that you are browsing from (don't know how to do that in windows).

Make sure to set the kernel parameter ForceHostP to f (last time I looked force-host didn't work, but maybe it has been fixed in the meantime).