Find the online product driver page for the mouse. Install the XP driver on the XP system. Do likewise for the Windows 7 installation using a Windows 7 driver if available. If the mouse worked before, you might check Device manager and see that the mouse is installed with a workng driver. Also in Control Panel the mouse should have adjustments available. If the mouse is not present, a driver problem may have occured.
Thanks for your reply.
I did that but still not working.
What I did was to plug the mouse in a different USB port.Result was that the add new hardware icon appeared and the mouse was working for 10 seconds and then the same situation!!!
Before it worked with no problems.