I can't assist you with installing that theme. I downloaded it and tried to install it but the process isn't straight forward.

I can recommend a link though, where the extensions are much easier to install.

addons.mozilla.org

Follow this link for themes
https://addons.mozilla.org/en-US/firefox/browse/type:2

Hope this helps.

 

Just to add on what Jack.Sparrow said, it would be best to get your themes, add-ons and extensions from the official Firefox website, that way you know it is safe for firefox and not an infection :wink:

https://addons.mozilla.org/en-US/firefox/browse/type:2

 

CrystalXP.net is safe stuff, but i want to install that theme because the isnt a offical (good) vista theme for firefox.

and all my PC now luks and acts like vista even though its XP so i wanted firefox 2 luk vista like.

 

There are a few vista themes on the official site, here are just a few links

https://addons.mozilla.org/en-US/firefox/addon/4626
https://addons.mozilla.org/en-US/firefox/addon/4988