i am mostly posting this as a courtesy to others who might be googling for the same info i was, and coming up empty...

i just got a new microsoft intellimouse explorer 4.0 to replace my old first get intellimouse explorer... and it required a software update to intellipoint 5.2... unfortunately the new intellipoint took away the option of assigning the "alt-tab" keystroke to one of the buttons...

i decided this was absolutely unacceptable. i wanted this mouse to REPLACE my old one, ie, i want it to work JUST LIKE THE OLD ONE DID. so, some hacking was in order.

open the intellipoint software and add a custom keystroke (doesnt matter what, the "a" key or whatever) and apply and exit...

then open regedt32 and go to key:

HKEY_CURRENT_USER\Software\Microsoft\IntelliPoint\EventMapping\

then look for the key under this branch as follows for the button you want to change:

4: wheel click
6: big/bottom side button
8: small/top side button

first, edit the "keystroke" value... to get alt-tab, enter 409 (hex)... if you want something else youll have to hack around to figure out what the keystroke is... but alt-whatever is always the base keystroke value + 0x400...

then change the keystroketext to whatever you want it to read (doesnt matter really) and viola! youre done!

(UPDATE) "piyo" has added more info on binding strange keystrokes to mouse buttons... see his response to this thread, or the re-post of his info. thanks piyo!