Hi,
-Were there any changes made to the computer prior to the issue?
-What is the make and model of the mouse?
Download the latest version of USB Optical Mouse drivers according to your computer's operating system.
-What is the make and model of the computer?
I would suggest you to try these steps and check.
Method 1: Hardware troubleshooter
Run the hardware troubleshooter on the computer to fix any hardware related issues.
Open the Hardware and Devices troubleshooter
http://windows.microsoft.com/en-US/windows7/Open-the-Hardware-and-Devices-troubleshooter
Method 2:
Usb Optical Mouse Driver Windows 7 32bit Download
Uninstall the Mouse drivers from the computer.
a.Click on Start and then type device manager in the start search box and press enter.
b.This will open the device manager.
c.Browse to Mice and pointing device, Right click on the device you see under Mice and pointing devices and click on Uninstall.
d.Restart the computer
After the restart, Windows will automatically try to download and install the latest drivers for Mouse. If this fails, then download the latest drivers for Mouse from the computer manufacturer website.
For reference:
Dell Optical Mouse Driver Downloads
Update a driver for hardware that isn't working properly
Let us know the outcome.