After I installed Visual Studio 2005 and started a new asp.net web project, I attempted to debug one of my projects and was presented with this message (Figure 1):

Figure 1: Unable to start program 'notepad.exe'.
The specified working directory does not exist or is not a full path.
Visual Studio then proceeded to fall out of debug mode (and even better, without recourse or even any suggestions on how to resolve this apparently very serious issue). Sigh.
After some file handle tracing using Iarsn TaskInfo 2003 I located the file handles coming out of Visual Studio 2005. Doing some additional file sniffing I came across the configuration files that were the problem.
It turned out there was a strange node in browsers.xml located at:
C:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\VisualStudio\8.0
C:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\DbgClr\8.0\browsers.xml
and in ExpansionsXML.xml at:
C:\Documents and Settings\Administrator\Local Settings\Application Data\Microsoft\VisualStudio\8.0\1033\ExpansionsXML.xml

I edited the XML and removed the notepad.exe "browser" and changed the value of the <default> element for the Internet Explorer entry to "True".
Returning to Visual Studio 2005, I launched debug on my asp.net application and the site properly launched in debug mode. Whew!
This was also preventing me from configuring my ASP.NET Configuration under the Website dropdown.
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Created 334 weeks, 21 hours ago