Uhm. Is that addon pack compatible with WoW 2.4.3? If I do a fast search on Google, I can only find ElvUI for WoW 6.x; that means it's only usable on WoD expansion.
But you could also check, to be sure, one of the addons in the pack: open the addon's folder, find the file named
<AddonName>.toc
(where <AddonName> is the name of the addon, for example Cartographer.toc) and search for the line "Interface", that should look similar to:
## Interface: 20400
Which in this case means its made for 2.4.0 version of the game (very near the 2.4.3, so it's ok).
To find other addon packs, try sites like http://www.wowace.com/ and be sure to check the "Files" tab when you selected an addon: there, search for the game version you seek (2.4.3, since you wrote into this section of the forum).