I don't remember if this is the forum where i saw someone having this problem (couldn't use two mice simultaneously on same station), but i'll post anyway.
TeamPlayer is an application built exactly to solve this problem. "It is the first commercial solution for working together on the same computer. Simply connect extra mice and keyboards to your usb ports, install the software and multiple cursors will appear on your screen."
NOTE: The free version supports only 3 users.
If you need more then 3 users you can buy the software.
The software can be "universalextracted" and works quite fine.
Reg entries:
HKCU\software\WunderWorks\
Enjoy!