Win98se, two drives, multiple partitions.
Partitions are backed-up individually with Microsoft Backup. Each backup execution produces a single archive file containing everything SELECTED for backup.  The restore program calls this file a "backup set".

A backup proceedes under one of two possibilities. (1) everything on the computer at one fell swoop (2) everything selected by the user. I always use (2). Each partition is done individually. Everything at once would take too long, would be too big for my backup storage, and would waste both time and space with a lot of data that changes very infrequently -- plus huge temporary project files.

This has always worked properly. Any part, or all, of a backup can be restored (to the same location or to a different location. I never had any REASON to try to restore the entire OS partition, but I had no problem getting individual files from the backups.

The disk containing the OS partition died. A new disk now has a new Win98se install from the Win98 installation CD. Because the backup "catalog" was on the OS drive, it no longer exist (except in the backup files themselves, I presume); the new catalog in the new install is empty. This requires a slightly different restore procedure:

(1) browse to find and select the backup file desired (the same as before)
(2) the program then SAYS "the catalog is empty for selected device" (because the original catalog no longer exists, the program does not know what is in the selected file). Originally the program went directly to (5).
(3) press the REFRESH button (not necessary when the catalog existed)
(4) program whirrs and hums for awhile while flashing a "creating temporary catalog" sign.
(5) after (3) and (4), everything is as normal. The backup set's contents are displayed in a browser window. One selects all, or any part(s), to write to where ever one wishes.

EXCEPT, if an OS partition backup is selected, after the whirring and humming, the program announces "The current media does not contain any backup sets" and quits. I have three backups of the OS partition. The program does the same thing with all, so I am as close to certain as possible that it is a built-in limitation, not corrupted data.

There are two possible reasons for the problem
(1) the program checks, finds Windows system files in the archive, and decides to quit. This does not happen when  the backup file is in the catalog, so maybe it is some kind of deliberate copy protection.
(2) I made the stupid mistake of checking the "backup system registry" option whenever I did a backup of the OS partition (but never when doing other partitions). This seemed potentially useful. It causes no problems under "normal" CIRCUMSTANCES (i.e. when the catalog exists), but maybe it is what triggers the restore program to quit.

The point of all this is that I need things from an OS partition backup, preferably the latest of the three I still have. Almost certainly the files are there, if only the archive could be opened and processed. Maybe someone know a way around the problem???