mouse problems

I am running Windows xp sp3 on all my computers.
Two of my computers are now having mouse problems.
Many times when I click the left button on the mouse, it will be a double
click.
I have checked the mouse settings and have tried to slow down the speed,
but the problem still is there. The mouse settings are still at single
click.

I tried to do download mouse drivers, but I keep getting "Driver Detective"
which I do not want, or to pay for.
Has anyone any advise to fix this problem?
Thank you.. Saywhat