If you are running Firefox 4 or higher on the "old" computer, then: (1) Open Help > Troubleshooting Information (2) Click the "Open Containing Folder" button next to "Profile Directory" (3) Copy everything to a safe place (please note that the copy of your profile does contain your browsing history and saved passwords, so best not to store in on media that you insert into public PCs) You can copy the bookmarkbackups folder to a USB flash drive, then on your new computer, import your bookmarks from there. See [https://support.mozilla.com/en-US/kb/Backing%20up%20and%20restoring%20bookmarks Backing up and restoring bookmarks | How to | Firefox Help]. (To clone your entire setup, after you install Firefox on the new PC, you can close it and replace the contents of the new profile folder with the contents you saved from the old computer. That doesn't always work, though.)

See also: *http://kb.mozillazine.org/Profile_backup *https://support.mozilla.com/kb/Recovering+important+data+from+an+old+profile