You can do this by creating a new hidden preference.

1. Type about:config into the location bar and press enter
2. Accept the warning message that appears, you will be taken to a list of preferences
3. Right-click somewhere in the list and select "New > String"
4. For the name of the preference type browser.cache.disk.parent_directory
5. For its value type the path to where you want to store the cache
6. Next locate the preference browser.cache.disk.enable, it must be set to true, if it is not, double-click on it to change its value

For more information on this see http://kb.mozillazine.org/Browser.cache.disk.parent_directory (the mozillaZine knowledge base is down at time of posting, but should hopefully be back up soon)

Thanks greatly, TonyE. I did exactly as you instructed, and after a reboot, voila! the cache directory appeared in my new location.

You've helped me save space on a very cramped c-drive.

I need help on this one being a neophyte. I want to move the cache to drive E :\FIREFOXTEMP (an sd card) Could someone please type out the EXACT command I should enter ?? I have confirmed that the second statement is set to true.

I wouldn't advice to use a SD card for the cache. Such a SD card has a limited number of writes and the cache is used very extensively, so a lot of writings will be done. That is why the disk cache is disabled in the portable version that is meant to be installed on such a drive. If you do not want to use the hard drive then you can consider to use a RAM disk instead.

we can do that by this method view images or visit http://www.auriolab.com/change-firefox-cache-location/

Thanks. Great info.