You can run more than one Firefox profile at one time.
You first need to create a new profile. You need to run the following in the run dialog or command prompt: C:\Program Files\Mozilla Firefox\firefox.exe -profilemanager
Make sure that each profile has a unique name. Check the “Don’t ask at startup” box.
Then, make another shortcut to Firefox. Copy/paste the current shortcut, then open up the properties page and go to the Shortcut tab.