After I restarted the computer after the installation, I received a message "Error Caused by a Device Driver". Everything's working okay, but I wonder if that NVIDIA thing screwed something up.

(The installation did create a new Restore Point in System Restore.)

I've seen this happen before. It's a minor mismatch between the actual NVidia hardware (your video board) and Microsoft's new NVidia graphics driver.

All NVidia chips in a given class, regardless of the brand of video board, are supposed to respond properly to a common driver, but in practice each manufacturer implements the chipset a slightly different way. That's why I prefer the manufacturer's version of the driver. You can roll back the driver to the last working version: Right-click on My Computer, left-click on Properties, then Devices, then Device Manager. Highlight the graphics adapter, go to Properties or Driver (I forget the exact order) and you'll find a button that will allow you to do a rollback. Don't be afraid to do this; in the worst case you can reinsert the graphics card's CD and get the original driver back.