X-Button Mouse Control: X-Mouse Button Control is a windows application to remap your mouse buttons.
This software is designed and written for Microsoft Windows XP/2003 x64 Edition but I have also, from version 1.5, built a 32bit version.
You are able to provide an application specific mappings, which means one application can use the mouse differently from another. This is useful for games which do not inherently support the extended mouse buttons, because you can map keys to each button.
A number of people that have looked at SharpKeys have asked me about remapping mouse buttons… I haven’t tried it but it looks like it would get the job done.