I'm surprised that the install didn't go right to your ".cab" files. Usually all the Windows setup files are placed in a subdirectory under the Windows directory when you are not given the install CD. In my case, they are in the C:\Windows\Options\Cabs directory. Usually, when a program asks for the Windows CD, it will give you the opportunity to specify a different location for the files.
Go to Start>Find> Files or Folders and type "*.cab" in the "Named" window and make sure the "Look in" windows is set for the C: drive. This should help you find where the Windows installation files are stored (if they are there). If you find several files called "Win98 xx.cab" then you have the right directory.
Once you know where they are stored, you can try the "tshoot.inf" thing again unless it doesn't let you specify a directory for the files. Let me know what you find. If this won't work, we can always try the registry fix for the other problem.