In order for you to play Half-Life 2: Episode Two on Windows with minimal graphics settings, your computer must meet the following requirements
Minimum:
1.7 GHz Processor, 512MB RAM, DirectX® 8.1 level Graphics Card (Requires support for SSE), Windows® 7 (32/64-bit)/Vista/XP, Mouse, Keyboard, Internet Connection
Recommended:
Pentium 4 processor (3.0GHz, or better), 1GB RAM, DirectX® 9 level Graphics Card, Windows® 7 (32/64-bit)/Vista/XP, Mouse, Keyboard, Internet Connection