John asked what I was going to ask. Does the mouse work in Word, in a browser, etc? IF the erratic control just in BIAB? I did not read the whole thread so I don't see if it is optical or a ball mouse. If it is optical, what is it sliding in? I have seen people use an optical mouse on top of a plexiglass desk top and the reflection from the plexiglass causes grief with the sensors that read the coordinates of the laser. Driver would be last on my list because most of them will work with just fine the generic PS2 mouse driver. Unless you bought a specific mouse like a Kensington Ball Mouse or something else with weird control points the stock PS2 driver will be fine. I have a Logitech on one, a Kensington on another, a generic USB mouse on the laptop running the BIAB and the only one I have had any grief on is this other laptop because it has one of those annoying touchpads and before I could disable the "double tap to click" feature I had to install the Dell specific driver for it. My very first guess would have been like a couple of others suggested, that the acceleration and pointer speed are too high and it is jumping across a whole screen from just one small movement.