Additionally this can be achieved using Raster Calculator:
SetNull( Not(IsNull( [EraseRaster] )), [OriginalRaster] )
Note that Not must be replaced with ~ in Arc 10.
I don't see who originally posted this solution, but thanks. It saved me from having to brush up on my raster calculator. Thanks.
I know this is really old, but this answer was perfect, EXCEPT how do you preserve the shape of the original raster? I performed this operation and the "new raster" was clipped by the extent of the "EraseRaster" when really, I'd like the extent of the "OriginalRaster".
I think you could just set the extent environment variable to be the extent of the "OriginalRaster" before performing the Raster Calculation and that should solve the issue.