I had a bad experience with faulty RAM module. I already had installed 512 megs of RAM and decided to upgrade. So I added another module of 1024 megs. Bad one. I got fatal NT bluescreen after a few hours. Then I rebooted but overnight my server application had crashed. The operating system could work in these conditions for days if left idle, though. I theorize that it's because the primary lower memory was good. I did not know enough about hardware then and assumed that the mem modules were not compatible with each other. But after testing the new ram, it turned out to be bad.
All files I had copied while the faulty ram had been installed had errors once in about every 50 megs. Now I faced the very serious problem: Most media files could not be automatically verified! As said previously Scandisk is useless in this situation unless the whole system experienced crashes. One needs to verify each file for errors specific to the file format with decoders that will report errors instead of concealing them!
The operating system and applications take up insignificant ammount of disk space in a clean, streamlined installation. With some work they can be restored to a working condition. What you have to worry about is your library of video and audio recordings, books, family photosm, or your work for other people.
Now to make my post useful for other users, here is the command that can help a little with video file verification:
ffmpeg -v 5 -i MEDIAFILE -f null - 2> STATISTICS
You need the command line version of ffmpeg. With this command it will decode the passed MEDIAFILE and output STATISTICS to a text file. The statistics will contain sort of decoding progress bar and what's important most (if not all) errors the decoder has attempted to conceal. The progress information can be easily skipped visually. Each mediafile needs it's own statistics file.
I can only recommend that you use formats that allow verification: lossless compression for audio (FLAC, Monkey's), pack your images in RAR (w/o compression), etc. Matroska may also have error detection, but I'm not sure.
I completely agree with your technical description. But I fail to see how this situation can be considered lucky in any way...