Problem with Firefox browser

I'm having trouble adding skins to my Firefox browser. I can't get them into the themes window. I had the same problem with the first release of Firefox-finally un-installed it and stayed with Firebird. Anybody gotta fix for this?

I'm using Windows 2000 Pro. OS. Also, I still have Firebird installed and working.

Found the problem. Tools>>options>>advanced>>tick the box for"allow web site to install software"

I've set it just long enough to get the themes I want, then un-ticked it.