Well, I have found some info for you....
but, as many others have done already, let us know what OS you are using. It will be much easier to give you the solution.
At any rate here is the solution for XP and Win2000
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout]
"Scancode Map"=hex:00,00,00,00,00,00,00,00,03,00,00,00,00,00,1a,00,00,00,1b,00,\
00,00,00,00
Cut and paste the above code into KeysOff.reg, then merge it with your registry. Next reboot your computer. The [] keys will then be disabled.
To enable the keys again, open Regedit and browse to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Keyboard Layout" and delete the key "Scancode Map"
Have fun!!!!
(now I have to reboot to enable my keys since I disabled them to test it)