[mlstier]

Mechanical Mouse: Remove the mouse ball, stick in a loop of tape, and replace the ball.

Optical Mouse: Short strip of opaque tape to block led's.

[cspackler]

Mechanical Mouse: Remove the mouse ball, stick in a loop of tape, and replace the ball.

Better yet, just place a small piece of tape over just one of the little wheels inside the ball compartment. End result, mose works fine, jst won't go "left"...