&gt; The AV software denied all disk I&#x2F;O. If you have nowhere to put data, and no access to data, then you don&#x27;t have a disk. You have a paperweight.<p>AV software does not deny all disk IO.  It just denies write access to a file very briefly and then goes on to the next file as the article stated it was a scheduled scan.<p>So you do have a disk but a few files temporarily can&#x27;t be written to (still can be read).  The program will get an error code from the write function and can just try to write again.<p>&gt; The disk I&#x2F;O didn&#x27;t fail. It was completely cut off by the AV program. There was no chance of it resuming until the scan completed, which could take far longer than the 5 minutes required to reboot the computer.<p>This is where you are incorrect.  And AV scan does not lock the entire disk for the duration of the scan.  It locks and releases each file as it scans them.  Fire up process monitor from sysinternals and look for yourself.<p>Tried it with my AV scanner with a manual scan.  Looks like mine doesn&#x27;t even do a lock on most of the files when doing a manual scan.  So at most the file just couldn&#x27;t be deleted.<p>&gt; My sole, singular point was this: Small programs are reliable programs. You can&#x27;t have bugs in what you don&#x27;t write.<p>I pretty much agree with you on that one.  Smaller programs are more reliable than larger programs.<p>&gt; What aggression do you feel I started with? I&#x27;m genuinely hoping to learn here.<p>I found it humorous that you saw aggression in my words and that wpietri saw aggression in your words.  Me, I just learned to tune out that sort of thing in other peoples posts.<p>&gt;  I said that the spectacular crash led to pinpointing the AV scan as the source of the issue.<p>And that&#x27;s what I was arguing about in my original post.  You know what Root Cause Analysis is?  If not read up about it here: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Root_cause_analysis" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Root_cause_analysis</a><p>My argument was that while the crash identified the AV Scan as a causal factor, it wasn&#x27;t the root cause.  From the wikipedia article: &quot;Though removing a causal factor can benefit an outcome, it does not prevent its recurrence within certainty.&quot;<p>The root cause was that the programmer didn&#x27;t handle the error code that his file was locked.  There are many more causal factors that can trigger the exact same outcome: indexing service, backup program, shadow copy, etc.<p>Unrelated to our debate, the medical company only blamed the AV software and the IT Staff.  Not one mention that their program had a bug.<p>The fact that their release notes warned against AV software means that they knew their program was deficient.  That&#x27;s what really pisses me off.