Here’s a quick how to on running Firefox 2 and 3 at the same time under Windows
- Right click the shortcut of the Firefox 2, click "Properties". Add "-profilemanager" at the end of the shortcut path. Click OK. Then run this shortcut to launch Firefox Profile Manager.
- Create a new profile, name it "firefox3". And uncheck the "Don’t ask at startup"
- Go to Properties of the Firefox 2 shortcut again, remove the "-profilemanager" and add "-p default" at the end