Here are the system requirements for World of Warcraft Cataclysm.

Windows XP/XP64/Vista/Vista64/7** OS (with the latest Service Packs or updates)
Intel Pentium 4 1.3 GHz / AMD Athlon XP 1500+
1+ GB RAM
NVidia GeForce FX / ATI Radeon 9500 video card
25 GB
4X DVD-ROM drive (Downloadable Installer also available)
Broadband Internet connection
Keyboard/mouse

Mac OS X 10.5.8, 10.6.4, or newer
Intel processor
2 GB RAM or higher
25.0 GB available HD space
4X DVD-ROM Drive
Broadband Internet connection