This page explains step-by-step how to adjust the mouse speed in Mac OS X. Many people have difficulty using a mouse because of the speed the pointer travels on the screen when the mouse is moved. This speed can easily be reduced to make the mouse more manageable.
Step 1: Open the "Keyboard & Mouse" window
Make sure you are in "Finder." If necessary, press Apple+Tab to cycle through the open applications until you return to "Finder."
Click on the "Apple" icon on the menu bar or press Ctrl+F2.
Click on "System Preferences," as shown in fig. 1, or press the down arrow key to highlight it and then press Enter.
In the "System Preferences" window (shown in fig. 2), click on the "Mouse" icon.
Step 2: Adjust the mouse pointer's speed
In the "Keyboard & Mouse" window (shown in fig. 3), make sure the "Mouse" tab is selected. If it is not, click on it, or press Ctrl+F7 to highlight one of the tabs and then press the left or right arrow key to select it. (Note: This window may display more options than those shown here, depending on the type of mouse you are using.)
Under the "Tracking Speed" header, click on the slider and drag it to the speed you want.
The mouse pointer speed changes straight away, so you can try different speed settings until you are happy with your choice.
When you are finished, click on the window's red close button or press Apple+W.