First try installing the latest drivers for your card.
1. make a system restore point just in case. go to start>right click computer>properties>system protection>check off necessary hard drives>create... and follow the steps
2.download the new drivers from here:
http://www.nvidia.com/content/drivers/drivers.asp you need to select graphics driver>GeForce 7 series>Windows Vista 32 or 64 bit (if you aren't sure which one you need go to start>right click computer>properties and look under "system type"
3. uninstall your old drivers. go to start>control panel>programs and features>NVIDIA drivers>uninstall/change, follow the steps. the computer should reboot and everything should look ugly. some windows wizards should come up, try to stop them if you can't its ok
4.install the new drivers you downloaded