[gries818]

Making a Firefox Extension backup is relativly easy. All of your extensions, bookmarks and personal settings are stored in your profile folder (see 2nd post in thread).

To backup just go into your profile folder and copy (not cut) the extensions folder to another location.

For a complete backup just copy your entire profile folder. That will save everything .

[Cornflake]

The profile folder is saved in C:\Documents and Settings\UserName\Application Data\Mozilla. Make sure that "Show hidden files and folders" option is selected in Tools > File Options in order to see the Application Data folder!

[gries818]

*Updated*