Hmm, that's really odd since scrolling is handled at a system level then passed to various apps via an API.
Either scolling support wasn't compiled into Firefox (not likely unless you compiled it yourself) or something odd is going on with the driver <-> app interface.
I'd suggest going to the laptop's site and downloading the latest drivers for the touchpad. It's likely that it's out-of-date.
Link with more info and a direct download from Synaptics if Compaq/HP doesn't have any updates.
Edit: Just to be perfectly clear here, there's no need for an extension to use the scrolling feature with Firefox unless you want to do something unusual like rotate through your opened tabs/history/etc. with the scroll. vertical and horizontal scrolling is built-in by default.