If you are using one of our clients and then do an update you are effectively replacing our client with IMVU's. Updates simply uninstall your current client and install the new one.
However, if you were to install multiple clients, say using my
TUTORIAL then the update will override any client installed in the default IMVUClient folder. If none of them are installed there than the update will simply install to that folder and you will have another version you can run.