In the Terminal, do this:
$ sudo su
# chmod 0000 /Library/Spotlight
# chmod 0000 /System/Library/Spotlight
# chmod 0000 /System/Library/CoreServices/Search.bundle
# chmod 0000 /System/Library/PreferencePanes/Spotlight.prefPane
# chmod 0000 /System/Library/Services/Spotlight.service
# chmod 0000 /System/Library/Contextual Menu Items/SpotlightCM.plugin
# chmod 0000 /System/Library/StartupItems/Metadata
# chmod 0000 /usr/bin/mdimport
# chmod 0000 /usr/bin/mdcheckschema
# chmod 0000 /usr/bin/mdfind
# chmod 0000 /usr/bin/mdls
# chmod 0000 /usr/bin/mdutil
# chmod 0000 /usr/bin/md

After a reboot, open a new Terminal and do sudo su to make a root shell, then:
# rm -r /.Spotlight-V100
# rm -r /private/var/tmp/mds
# exit

Why use chmod? This hack can be reversed by repairing permissions.