I use ATi Tool (not ATi tray tools!) for my 7950GX2. It states it's compatible with all Nvidia cards so your 8800 should be covered!
With it i can clock the card, monitor temps and see voltages. It even has a 3d test window where it will check for graphical faults as an overclock is applied and increased!
Here's a full list of what it can do:
- No limits overclocking.
- Support for overclocking for NVIDIA cards.
- Finding maximum core and memory overclock by rendering into a Direct3D - window and scanning the output for visual artifacts.
- Temperature monitoring and fan speed control (on supported cards)
- Removal of Catalyst overclocking lock for 9000/9200/9550/9600 series.
- Artifact scanning mode to test for stability.
- Loading a predefined clock profile on Application/Windows startup.
- Hotkeys that can be used any time to load clocks from a profile.
- 3D application detection (Direct3D 8, Direct3D 9, OpenGL) to overclock your video card only when required.
- Gamma control
ATi Tool doesn't have a frame counter though but (as recommended above by Tombo) i use FRAPS for that!
Give those a try!
gt