Backup and Restore Center: Error Restoring (0x8100001A)

I am unable to restore files backed-up via Backup and Restore Center, "Backup
Files". I backed up all possible files from my old Vista installation (not
knowing it wouldn't include executables--there goes all my archived setup
files for purchases programs, but that's another story) to an external USB
hard drive. The files were verified at backup.

I was able to restore these files to a new Vista installation via the
Advanced Restore option ("From another computer"). However, there was a
problem with that installation and I reinstalled a second time the next day
to my current installation. However, I now cannot restore files. As far as
I can tell, nothing has changed, although something *must* have. The
external drive is given the same letter, and I've even tried restoring while
logged in under various different possible usernames.

The restoration goes all the way to the "preparing screen" (this is whether
I choose to restore the full backup, or choose some folders, or choose some
individual file) and then aborts with this message:

Restore did not finish successfully. Error code:

The backup file could not be found. Check your hardware
configuration or restore from a different backup. (0x8100001A)

I've looked all over the net. There's one other discussion here with this
problem, it remains unresolved as of this posting. I noticed that a similar
error could occur with XP's backup and restore app.

Manually unzipping individual files from the backup isn't really an option
because a great many of the files I need were split and spanned. In some
cases I've been able to concatenate the files to get the original, but the
proper order can be difficult to discern (pieces of the file are placed in
the zipped files all under the same name--complicating matters greatly when
unzipping them).

I've even tried using a hex editor to look at the catalog files to try to
get an idea of what the restore program might be looking for, but it wasn't
that easy to read the file.

Help! Can I also gripe about the fact that I've never really needed to use
MS support in my many years of using their products until now, and now when
I've bought Vista Ultimate, no less, I discover that I had only 90 days of
support from the date of activation? Grrr.