IntelliPoint 5.0 is a downgrade :(

Maybe someone can help me with this its why i came here but here it is. So i got a MS desktop pro and it comes with intellipoint 5.0 i had a ms wireless opti mouse befor witch was awsome worked great (other then battery life was short as all hell) well when i got the new mouse and keyboard of course i upgraded the software from my original intellipoint 3. what ever to 5.0 well guess what 5.0 dosnt have... the ability to reasign the mouse buttons to any key or key comibination on the keyboard. Witch sucks for gammers heh. SO my qustion is dos anyone know if there is a tweak for intellipoint 5.0 to asign ANY keyboard command to the mouse buttons. heh thinking about reinstalling and puting 3. what ever back in but i got a bad feeling though that i wont find the same mouse on the list and not all the functions will work.