Crysis Warhead (click to enlarge)

The EA Store has revealed Crysis Warhead’s system requirements..

CPU: Intel Pentium 4 2.8 GHz (3.2 GHz for Vista), Intel Core 2.0 GHz (2.2 GHz for Vista), AMD Athlon 2800+ (3200+ for Vista) or better
RAM: 1GB (1.5GB on Windows Vista)
Video Card: NVIDIA GeForce 6800 GT, ATI Radeon 9800 Pro (Radeon X800 Pro for Vista) or better
VRAM: 256MB of Graphics Memory
Storage: 15GB
Sound Card: DirectX 9.0c Compatible
ODD: DVD-ROM
OS: Microsoft Windows XP with Service Pack 2 or Microsoft Vista
DirectX: DX9.0c or DX10

As you can see, they are almost all the same as Crysis except for HDD space..

Source: EA Store.