how do i disable the tabulator key?
 

how do i disable the tabulator key [two arrows above
the capslock]. it is useless to me, and acidentally
hitting it causes all sorts of problems.

Edit the file
/usr/share/X11/xkb/symbols/pc
You don't say your distro (add it to your profile as I've done), so it might be somewhere in /etc instead.
You'll see a line
key <TAB> {[Tab, ISO_Left_Tab]};
Alter to
// key <TAB> {[Tab, ISO_Left_Tab]};
and that should do it. You have to log out and log in again for it to take effect.