GPU-Z is a light and free utility which will give you all the information you need about your graphic card and GPU. GPU-Z support NVIDIA and ATI cards, displays adapter, GPU, and display information, overclock, default clocks, 3D clocks (if available), and validation of results.

GPU-Z Main Features:
Supports NVIDIA, ATI and Intel graphics devices
Displays adapter, GPU and display information
Displays overclock, default clocks and 3D clocks (if available)
Includes a GPU load test to verify PCI-Express lane configuration
Validation of results
GPU-Z can create a backup of your graphics card BIOS
No installation required, optional installer is available
Support for Windows XP / Vista / Windows 7 / Windows 8 (both 32 and 64 bit versions are supported)