If you have Windows 2000 installed on a laptop with a port replicator or docking station, your mouse pointer may jump or behave erratically.
Most laptops use a touchpad or 'nub' pointing device which uses a 3-byte packet to communicate. Some wheel mice use 4-byte packets. When both are connected at the same time, the BIOS may misinterpret the string.
Your options are:
1. Get an updated BIOS that fixes the problem.
2. Use a 2 button mouse.
3. Connect your serial mouse via a serial-to-PS2 port converter.