Rated 4 out of 5 stars

Dhrubajyoti Gogoi, I had a similar problem when installing some Add-ons, until I disabled my Firewall, then all Add-ons installed O.K.
Julien, not true at all. I don't notice any CPU useage increase or FF being slow in any way or form!
Maybe you should upgrade your old 486!! Adding more RAM will help, too. :)

This review is for a previous version of the add-on (0.8.20090920.2).