I have installed Gatherer a couple times over and i can not seem to get it to open at all. I did read that other guys post and tried moving the folder to my C drive however it still will not come up nor does it show in my Add-ons tab ingame.
if it isn't showing up in the addons tab in game, then you are not installing it properly. in your wow/interface/addons directory, there should be a subdirectory inside it called Gatherer, and there should be files (including one called Gatherer.toc) and folders inside of it.
Make sure your ZIP program is properly extracting the folders as described above.