Hi Korsoul,

Addons must be installed to a specific directory. Depending on your operating system they would go one of these two places by default:

Vista - C:\Users\Public\Games\World of Warcraft\Interface\AddOns
XP - C:\Program Files\World of Warcraft\Interface\AddOns

Also ensure you have not placed the .zip file directly into the AddOns folder. You need to open the zipped file and extract the standard folder in with the rest of the WoW addons.

Q u o t e:
THE MOST COMMON ERROR is that the unzipper program embedded them into an extra folder layer. If you have any questions about whether your addons are embedded one folder too deep, post a path for the .toc file of each addon

Windows XP:
C: \ Program Files \ World of Warcraft \ Interface \ AddOns \ MODFolder \ ModName.toc

Windows Vista:
C: \users\public\games\World of Warcraft \ Interface \ AddOns \ MODFolder \ ModName.toc

INCORRECT EXAMPLE:
C: \ Program Files \ World of Warcraft \ Interface \ AddOns \ MODFolder1.23.456 \ MODFolder \ ModName.toc < --- is NOT correct, and the addons will not load properly.

There should only be one path-step between the AddOns step and the .toc step, and it should be the name of the addon (most usually). Look very closely at the directory structure, make sure that the addons folder is in the proper place. If you have any questions about whether your addons are embedded one folder too deep, post a path for the .toc file of each addon.

Pay particular attention to this part. If you've extracted the file into the correct AddOns folder it is likely you have a folder with several numbers/letters at the end of it, which as described above would be incorrect.