GPU-Z is a lightweight utility designed to give you all information about your video card and GPU.
It's so simple to use, you don't need documentation.
Just download and run the binary.
Support NVIDIA and ATI cards
Displays adapter, GPU and display information
Displays overclock, default clocks and 3D clocks (if available)
Validation of results
No installation required
Support for Windows 2000 / XP / Vista / Windows 7 (both 32 and 64 bit versions are supported)
.. and yes, the author of CPU-Z has granted permission to use a name similar to his product. Thanks Franck.