Okay, here's the goods. Sorry to keep you in suspense!

Basic idea is archive.org, but the following info is a bit more specific...
Unless they are mislabeled, all volumes 1-51 are present at
http://www.archive.org/search.php?qu...ard%20Classics , with the following exceptions:
TXT files
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Missing #1,34
PDF files
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Missing #1, 34, 38, 39, 40, 42
Notes:
* The missing pdf volumes may have scans available under the ftp directory.
* The missing text volume #1 was part of the Portable HC.
* Volume #34 should be available in HTML at Bartleby.
* Text files look like raw scans, but not too bad. They should be good enough for reading purposes.
Sorry, no time for more analysis, but this should be helpful.
BTW, as an aside, that site also led me to this title, found in various formats at manybooks.net...
http://manybooks.net/titles/arbert10481048910489-8.html