It seems previous Spotlight disabling method that worked in Leopard, no longer works in Snow Leopard.
How can I disable Spotlight in Snow Leopard?
Open up terminal app and type in:
mdutil -a -i off
mdutil -- manages the metadata stores used by Spotlight
-a applies for all volumes
-i turns indexing on or off
For more help type in terminal:
If you prefer not to use the Terminal, you can use this paid software Spotless.
It's not exactly "disabling", but you could always add your root drive to the Privacy list in Spotlight.
Either that, or kill the mds and mdsworker processes.
Warning : Some apps are bound to break.
Here’s an old thread on SuperUser which covers removing the Spotlight completely from the menubar. Since your question isn’t clear on that point if you really want to deactivate it or if you just want to make it disappear -simply have a look here - maybe you like this solution.