I installed FF 2.0 and noticed one of my extensions would not update. So digging into my old FF 1.0 notes from 2004 I found my old extension fix. Here it is as follows.

Download the extension that will not update to a folder. Rename the extension from .xpi to .zip then with 7Zip unzip it.

You will have three files, chrome, install.js, install.rdf. Then open the install.rdf with Notepad, scroll through to this line <em:maxVersion>1.9</em:ma­ xVersion> and change 1.9 to 2.1 or higher, this line is in two places. Save the file.

Then with 7Zip select the three files and add to archive, but use a .xpi extension instead of .zip.

Then install into Firefox 2.0 as normal by dragging it into the Add-ons box...

Thanks for posting that Arctos!