Over the last couple of days my display was going dark after about a minute if i didn't move the mouse or have a video playing. Checked Power Options / Advanced settings to see if maybe some program (or my girlfriend) had changed the "Turn Display Off After" ... "Never" setting, but it was OK. And, the Sleep setting was still on Never, too.

After some head-scratching i remembered downloading and installing a new Windows theme recently. So, went to Personalize / Screensaver and there it was - the Blank screensaver set to run after 1 minute! Changed that and problem solved.

Posted this so others will know that (maybe) a Windows theme pack will change more than one setting on your computer. Frequently, a Windows theme comes with its own Windows sounds so when you begin using the new theme a "ding" sound suddenly becomes a "clang" and so on. But, this was the first time i've encountered a screensaver change.