What computer can play dayz and ARMA II

Well firstly you need Arma II to Play DayZ because it is a Mod for Arma II so there's one and also check if you computer matches these requirements
Minimal PC Requirements

• CPU: Dual Core Intel Pentium 4 3.0 GHz / Intel Core 2.0 GHz / AMD Athlon 3200+ or faster
• RAM: 1 GB
• Video Card: NVIDIA GeForce 7800 / ATI Radeon 1800 with Shader Model 3 and 256 MB VRAM or faster
• OS: Windows XP

 Optimal PC Requirements

• CPU: Intel Core 2.8 GHz / AMD Athlon 64 X2 4400+ or faster
• RAM: 2 GB
• Video Card: NVIDIA GeForce 8800GT / ATI Radeon 4850 with Shader Model 3 and 512 MB VRAM or faster
• OS: Windows XP or Vista

Source From Official Website