I (manually) defragmented my C:\ drive, and now the headphone jack doesn't work. When I plug in headphones, I just hear a constant static buzz and no audio. I've tried this with 2 separate pairs, both of which worked just fine on this computer before the defrag, and I've also confirmed that they work on other devices.
Apparently the drive is set for automatic defrag once a week, and apparently it did an automatic defrag 3 days ago with no issues. It's the manual defrag that seems to have messed up the jack. As far as I can tell, though, the defrag didn't cause any other problems.