We found that we couldn't run a stand-alone on a computer that also used the production system, but we do have a test copy running on a separate machine. The test machine is a backup server that I access via terminal services, effectively allowing me to run both at once in different windows. Very insightful.
For a good description of how to set up a stand-alone copy for testing or training, go here:
http://www.istechforum.com/cgi-bin/YaBB.pl?num=1153185297/11#11