Unfortunately, this is becoming more and more commonplace. I've seen it too many times when I go to look at someones PC and they have no AV, or the defs are out of date by months, or in one case, 1 1/2 years.
A decade ago, you could barely get away with relying on the "automated scans" to take care of everything. That's not the case nowadays. Owning a PC in today's hostile web environments demands vigilance on your part.
One of my Wife's family members had a PC with approx 700 infections on it. They did not have a Windows Disk and the recovery sector was corrupted, so my options were limited. It took a recovery boot disk approximately 6 hours to clean it.