File > Import and Export, and go through the Wizard.

It will allow you to export each version of favorites to a file, which you can then copy over to the other PC's and import.

You can use Firefox's Import option in the File menu to do the same.

To export Firefox's bookmarks you will have to goto Bookmarks > Manage Bookmarks, and then File > Export.

You will probably get quite a few duplicate entries this way. I don't see anyway around that.

I hope this helps.