If you would like to test drive Firefox 3.1 beta without uninstalling your stable Firefox 3.0 browser, download the portable version. PortableApps.com has released Firefox 3.1 beta web browser portable application that run as a standalone executable. Portable applications does not require any installation and they can also be launched from removable media like USB drives.
Downlaod Mozilla Firefox Portable Edition 3.1 Beta 1 from PortableApps.com
What you said is right nice trick to test Firefox 3.1 beta I will try this
Its a great tip to experience Firefox 3.1 beta.
Thanks.