Modern Warfare 2 System Requirements
Here are the system requirements for the PC version of MW2. If you are able to run Call of Duty 4 and/or World at War on your PC, you shouldn't have any problems with Modern Warfare 2, as the requirements are almost the same.
Minimum System Requirements
||Microsoft Windows XP, Windows Vista and Windows 7 (Windows 95/98/ME/2000 are unsupported)
||Intel Pentium 4 3.2 GHz or AMD Athlon 64 3200+ processor or better supported
||1 GB RAM
||256 MB NVIDIA GeForce 6600GT or better or ATI Radeon 1600XT or better
||Microsoft DirectX(R) 9.0c
||12GB of free hard drive space
||100% DirectX 9.0c compatible sound card
||Broadband connection required for Multiplayer Connectivity. Internet Connection required for activation.