I still have a lot of spatial data that was created using ESRI ArcView 3.x, and I continue to use 3.x because I have a wealth of extensions that do the things I need to do.  One problem with creating shapefiles with 3.x is that projection files (.prj) are not automatically created along with the shapes, so there is no spatial reference.  I normally end up with a whole directory full of shapefiles without .prj files.  I finally broke down and searched arcscripts.esri.com for an easy way to define the projection of all of those shapefiles in the directories.  I ran across Batch Define Projection by Owen Evans, downloaded it, and tried it out.  Works wonderfully.  It creates a custom toolbox and includes a few different handy scripts, including a batch define projection.  Run the script, point to a bunch of shapefiles, choose your coordinate system, and you’re done!  Why didn’t I look for this a long time ago?  Highly recommended.