Thx ady. It might not be called a low level format anymore, but that's what it is.... what I'm doing a "secure erase" (DOD specs) which writes to each and every space on the HDD, reads it back, then writes it again. This obviously takes a long time on the huge drives of today (even a dskchk takes a lot of time and it ignores unused areas).
And I am 98% it does not indicate a hardware problem (other than the bad areas I know are present); rather, according to Seagate's website, this general process can often discover bad areas on the drive that other procedures will not (ie, dskchk, which, by the way, apparently marks files "good" when it is run, even if it does not fix or cannot find actual corruption), and then the secure erase "repairs" the area by marking it bad and replacing it with "extra" areas on the drive that are there solely as replacements to bad areas.
As for Avast, I also understand "decompression bomb" doesn't mean the file is corrupted, only that Avast can't or won't take the time to decompress to examine the file, it's just I didn't remember if that was "the exact" phrase Avast used. Interestingly, and it was a surprise to me, since Avast has to read/open files to look for viruses, an "undocumented feature" is that it does find corrupted files when it tries to look for viruses. And again, Avast found these issues when dskchk did not.
It's been 20 yrs since I was actually employed as a programmer so please excuse if my "lingo" is out of date, but what I am doing is a valid effort. My HDDs are old and are likely to be close to failing (note, only 1 of the 2 RAID1 drives seems to have problems, and they are intermittent at that), but my primary concern here is to "clean up the bad HDD" so I can restore to it from an old backup before I migrate to new HDDs, all the while keeping the other -RAID- HDD in "reserve"/"preserved" in case my methodology for fixing and migrating my OS/HDD fails.
So my #'d questions remain: in essence, after I restore from an older backup, I still need to check for corrupted files, and I need to fix any Vista software issues, before migrating to new HDDs.
And fwiw, Vista is crap, but I don't want to migrate to 7 because it is essentially obsolete, and 8 is crap... you know MSFT, they cycle "crap", "good", "crap", so I'm waiting for Win10, which they have no choice but to "get correct" (or they will have taken a major step toward obsoleting themselves?), then I'm migrate to completely new HW and SW.