Well... you can check the raster's properties by right-clicking on it in the table of contents and selecting properties, then click around. Alternately, r-click and see if you can open the table... if it is greyed out it is a floating point raster... aka ... no table raster.
A raster can have a coordinate system defined, it will either be a Geographic Coordinate System, GCS, or a Projected Coordinate System (PCS). GCS's have units of decimal degrees... pretty useless for most analytical things or most things requiring area, distance, length useage. PCS's have units of meters (except in the U.S. for the most part, still on the feet ). So when you specify the number of cells to expand (shrink) you should know that 1 cell is equal to X meters since you probably have no idea what 0.00833333 degrees represents (and it is not a constant either).
Once you can ascertain what type of raster data you are working with, then Expand and Shrink will work as designed if you adhere to basic rules and are aware them (no spaces in paths, keep paths short, keep file names short, if you want anything other than an ESRI grid, then you have to specify an file extension.... I could go on, but I won't)
Report back if you are having difficulties still.