Here are the Sleeping Dogs system requirements (minimum)
CPU: Core 2 Duo 2.4 GHz or Althon X2 2.7 GHz.
OS: Windows Vista Service Pack 2.
VIDEO CARD: DirectX 10 or 11 compatible Nvidia or AMD ATI card, ATI Radeon 3870 or higher, Nvidia GeForce 8800 GT or higher.
FREE DISK SPACE: 15 GB.