In order for you to play Arma 2 on Windows with minimal graphics settings, your computer must meet the following requirements
OS *:
Windows XP or Windows Vista
Processor (CPU):
Dual Core CPU (Intel Pentium 4 3.0 GHz, Intel Core 2.0 GHz, AMD Athlon 3200+ or faster)
Memory (RAM):
1 GB RAM
Graphics Card:
GPU (Nvidia Geforce 7800 / ATI Radeon 1800 or faster) with Shader Model 3 and 256 MB VRAM
Hard Drive:
10 GB free HDD space
In order to play Arma 2 on Windows with maximum graphics settings, you need a computer with a configuration no worse than the following
OS *:
Windows XP or Windows Vista
Processor (CPU):
Quad Core CPU or fast Dual Core CPU (Intel Core 2.8 GHz or AMD Athlon 64 X2 4400+ or faster)
Memory (RAM):
2 GB RAM
Graphics Card:
Fast GPU (Nvidia Geforce 8800GT or ATI Radeon 4850 or faster) with Shader Model 3 and 512 or more MB VRAM
Hard Drive:
10 GB free HDD space