I have problems with Define Projection tool. I have Windows 7. and ArcGIS 9.3.1 with SP2. I have to define projection (spatial reference is undefined) for standard Croatian tif+tfw rasters and both ArcMap and ArcCatalog crash during that action. I am using MGI Balkans 5 coordinate system, which already exists in software. Project Raster tool works fine, for now.