Hello Vrajjshah,
Thank you for posting your query on Microsoft Community forum.
As per the issue description it seems that you are unable to use your mouse after upgrading to Windows 7. So there might be a chance that the drivers of devices are not updated so you might be facing the issue.
I would suggest you to try the below mentioned methods and check if it helps.
Method 1:
Follow the troubleshooting steps from the Kb article and check if it helps.
Troubleshoot response failures in wireless keyboard or mouse
http://support.microsoft.com/kb/838398
Method 2
If issue still persists you need to update the drivers and for that you may try the steps provided in the following article and see if it works for you.
Windows comes with drivers for many devices, such as printers, displays, keyboards, and TVs. A driver is software that a device uses to work with your PC. Every device needs a driver to work with your PC. So, in many cases, you can plug in a device, and it’ll work automatically.
If still issue persists you may try to update the drivers from the manufacturer's website and the link you may refer is provided below.
Hope this would help. If issue still persists post back with current status of your computer and result of the proposed suggestion, we will be happy to assist you.
Thank you.