In order for you to play Half-Life 2: Deathmatch on Windows with minimal graphics settings, your computer must meet the following requirements
Minimum:
1.2 GHz Processor, 256MB RAM, DirectX 7 level graphics card, Windows XP, Mouse, Keyboard, Internet Connection
Recommended:
2.4 GHz Processor, 512MB RAM, DirectX 9 level graphics card, Windows XP, Mouse, Keyboard, Internet Connection