Reply #2

...the mouse and software (do you have a backup mouse to use?) and then reboot and reinstall.

Uninstall the software from control-panel->programs-and-features and then uninstall the device from control-panel->device-manager. I think this is the place to download the correct drivers and software: http://www.microsoft.com/hardware/en-us/d/wireless-intellimouse-explorer-2.0

I've had trouble sometimes with windows not recognizing the mouse when it was moved to a different USB port.

Another thought is to try another mouse in the same and a different port. (I'm assuming this is a USB mouse.) Try using a different port, preferably one on the back of the PC. There may be a cable between a front panel USB and the motherboard that has worked loose. I am always most suspect of front panel ports.

HTH