To be able to use Iowa data from the ISU orthoserver, you need our .ogc files.Get them from our public ftp server. Use a web browser, go to ftp.gis.iastate.edu and navigate to ISUGIS/Utilities/ArcView/extensions/WMS_client.
Get the ARC3WMS_Beta_2_0_1.exe and the WMSIowaExamples.zip files.
Run the executable to install the software, choose the default location.
You could also get the WMS client right from Refractions Research -  http://www.refractions.net/arc3wms/
If you chose to install the software in the default spot, make an Iowa folder to hold the examples  - C:\Program Files\WMSClient\Examples
Unzip the Iowa examples to the location you just made in the Iowa folder, probably in the default location for the software.
It really doesn't matter where you put the examples but if you keep it in the software folder it is more tidy.

Start ArcView3 and turn on the WMS extension, which was not there before you installed the Refractions extension.
Add a dataset that you know is projected to UTM 15, NAD83.  Anything from the Iowa DNR should work.  Zoom to an area roughly county sized or smaller.
This is to make the image draw go faster, it will work at smaller scales but will take a while.
Add a dataset as an image and navigate to the Iowa examples location and choose one of the .ogc files.  For instance, the 2006 image.
It should add to your layer list with no problems.  Turn it on.  The imagery for that location should pop up.  If not, zoom in or out to trigger the redraw.