Visual Studio .NET has higher system requirements than the Common
Language Runtime itself. To install the runtime and run managed code,
you only need Windows 98 or above. In fact, even version 2.0 should
install and work mostly correctly on Windows 98 and above.
What you have seen is a classic example of a developer who wrote code
(in any language, in this case VB.NET) that works on Windows XP, but
has a bug that prevents it from working on Windows 98.
I don't recommend that you try using a debugger on Windows 98; that is
indeed painful. Your best bet is to first of all make sure that you
are running "debuggable code" which you can generate in VS by selecting
"Debug" from the drop-down at the top. Then copy the exe and the pdb
file onto the Win98 machine to a known and simple location like the
root of you C drive for example. Then open a command window by running
"command", navigate to where you put your exe and run the exe. Then,
when the exe crashes, click on the "OK" button to Terminates the
application. You should see a full stacktrace of where the problem
occurred on your command window now.
Chances are really good that the bug is in your code and not a problem
with VB.NET, so this stacktrace will help you to figure out what you
may need to change to make your code 9x compatible.