Just getting back into GIS after being out of the game for a few years and I was wondering if anyone has any suggestions on why I am having trouble converting a raster image to a polygon in ArcGIS 10? I downloaded the data from PASDA, a Pennsylvania clearinghouse run through Penn State, and it displays fine however I keep getting an unknown error message (ERROR 999999) when I try to run the geoprocessing tool to convert it from a raster image to a polygon. Do I have to change the type of raster extension to get a better result, such as changing from .img to .tiff? Also does cell size affect the outcome of the conversion? Any help would be appreciated.