The cheapest graphics card you can play it on is an NVIDIA GeForce 510. You will need at least 4 GB of free disk space to install Half-Life Deathmatch: Source. An Intel Pentium 4 2.00GHz CPU is required at a minimum to run Half-Life Deathmatch: Source. The minimum memory requirement for Half-Life Deathmatch: Source is 1 GB of RAM installed in your computer.
Half-Life Deathmatch: Source will run on PC system with Windows® 7 (32/64-bit)/Vista/XP and upwards. Additionally it has Mac and Linux versions.
Minimum System Requirements
CPU
Dual core from Intel
RAM
2 GB RAM
OS
OS X 10.5.8
Graphics Card
nVidia 320M or higher, or Radeon 7000 or higher, or Intel HD 3000 or higher