.hgt is SRTM data extension. you can directly export this kind of data to .dem (USGS) from Global Mapper (registered only)
1. just click File – Export Raster and Elevation Data – Export DEM – OK
after that just load your ArcView
2. move your cursor to File – Import Data Source – Select USGS DEM – OK
3. then create contour from Surface – create contour – insert your interval kontur needed..
4. final step is convert to shapefile, just move your cursor to Theme – Convert to shapefile..choose where you want to save your .shp (complete with tabular data).
after all steps, you could modifies your data..
good luck yooo..:)
a. In step 4. make sure your “contour” in active position..select it for activated