I am having problem with projecting my counties which are in GSC_1841/Hermannskoegel to WGS_1984 in ArcGIS 9.3. I tried the basic "project" with importing the existing coordinate system but that's pretty much it and nothing happens. Somebody advised me that first I have to change the ellipsoid manually, and then do the transformation using predefined seven values/numbers. Could anyone be more specific? Thank you in advance.
EDIT: Old Yugoslavia is the country.