You need 6GB of RAM minimum, too.
Full Article
http://www.eurogamer.net/articles/2013-10-08-mega-textures-push-call-of-duty-ghosts-on-pc-to-50gb
Want to play Call of Duty: Ghosts on PC? Then you'll need 50GB of space on your hard-drive.
Nvidia published the minimum and recommended system requirements for the upcoming shooter on its website, and they reveal the game comes in at a whopping 50GB.
Also of note: you need 6GB of RAM at a minimum to play.
Those minimum specs in full:
OS: Windows 7 64-Bit / Windows 8 64-Bit
CPU: Intel Core 2 Duo E8200 2.66 GHZ / AMD Phenom X3 8750 2.4 GHZ or better
RAM: 6 GB RAM
HDD: 50 GB HD space
Video: Nvidia GeForce GTX 550 Ti / ATI Radeon HD 5870 or better
Sound: DirectX Compatible Sound Card
DirectX: 11
Internet: Broadband connection and service required for Multiplayer Connectivity. Internet connection required for activation
And the recommended specs:
Video: Nvidia GeForce GTX 780
Full Article
http://www.eurogamer.net/articles/2013-10-08-mega-textures-push-call-of-duty-ghosts-on-pc-to-50gb