Regarding the problem of ArcCatalog and ArcMap not "seeing" the presence of .txt, .cvs, etc. files:
Have you ever gotten verification that the .dll registration had a positive effect?
It doesn't sound like David Fann (in this thread) applied it, but has anyone else that you may have helped, external to this forum?
Do you think the Windows XP Home operating system is a factor?
I have two distance education students who are having the problem described by David, above, and Alyssa, below in this thread.
They are running version 8.3 of ArcView. They both have applied SP3.
I've had them check the settings in ArcCatalog that you refer to above.
As well as the Control Panel settings you mention.
One of them has reinstalled the ArcGIS/ArcView software. His OpSys, etc., upgrades are up to date, too, as per Alyssa's posting below. (Do you have any idea which of what Alyssa did was the magic bullet?)
The only thing I have not had them do is the .dll registration that you mention.
I'd appreciate your thoughts.