What do you know today that you didn't know yesterday?

[Angrboda]

I learned how to repair a Windows system with corrupt system files. Both my desktop and my testing system have been afflicted recently. There was a bad stick of memory in the desktop, but even after replacing there have been issues. The first symptom was that Alt-tab stopped working. After replacing the memory stick, reinstalling the video drivers fixed that. But even with good ram, Ctrl+A stopped working, requiring the same fix. I haven't tested the memory on the testing system, so that's a possibility. It isn't saving my changes to the power plan scheme, resulting in the screen turning off every 20 minutes, no matter how many times that I tell it not to do so.