The other day Avast antivirus released an update which caused many respectable websites, including Yahoo.com, to be designated as malware. This was a temporary inconvenience for many, but for a few it is an ongoing disaster. My grandmother is one such.
Like many elderly people she has a limited knowledge of computers and she tends to trust what her security software tells her. Her Avast started telling her her computer had multiple viruses and naturally she started running a full system scan, in this case a boot time scan. Unfortunately she also trusted it when it started telling her most of her OS files were infected and she proceeded to let it delete them.
After a while she decided something was wrong and called me. I went over to assess the damage and found her OS would no longer boot except in safe mode. After six hours of trial and many many errors I came to the conclusion that it could not be saved. Even an OS reinstall is not an option at this point because her restore partition was also corrupted. Not a fun day for her or me.