If you are on a Microsloth PC you do not need to ditch what you are already using.
Check out http://portableapps.com/.
It is designed to run useful software from a USB memory stick without installing anything on the PC, but works just as well from an location on your PC hard drive, or attached storage. If you want to uninstall one of it's components, all you do is delete the folder it is in.
It also means you can have different versions of the portable version of firefox saved in different folders. The PC will only run one version at any one time, but they save things such as cookies in their own separate folder, so what you do on one version cannot mess up what you do on a different occasion when you are running the alternative version.
Portable Apps also allows you to run a stack of useful programmes that will do most of the things we need to do on a routine basis and extra options are being added on an almost daily basis.
Quack!
GtD.