Ten years ago IBM created a box that you could plug into your computer that would reduce the effect of tremors on the movement of the mouse. The Assistive Mouse Adaptor was made by a company called Montrose Secam Ltd. Their website is down and I think the company and the box is no longer available.
There are currently no tremor-reducing software solutions for Windows 8 or Windows 8.1
Windows XP / 7 / Vista
SteadyMouse is free software that works with these versions of windows and can make using a mouse significantly easier if you have a tremor. You can download the latest version of SteadyMouse for free.
You can also try slowing down the movement of the pointer in Windows, enable “snapping” so the cursor jumps to targets such as buttons, increase the size of buttons and other targets or try a different mouse or specialist pointer.