I’m fully patched; also run a dual boot Vista and don’t have this problem there. I don’t use any screensavers.
I have my XP Power Options set to turn off the monitor, usually after 15 minutes of inactivity, but I’ve experimented trying to solve this problem. It has happened in the past, gone away for a long time, and now has reappeared, so I think that a Windows patch somewhere along has brought it back. After booting, the power WILL turn off on the monitor after the prescribed time, but somewhere during the day, “something” deactivates it and I’ll come back to the machine with the screen NOT dark. If I open Power Options and re-select the correct drop down, it will work again for some undetermined period of time. I don’t think it’s Avast or some other program updating itself or I would be able to catch it. My only other “real” scheduled task is my overnight backups but this also happens during the day.
For example, I’m getting ready to leave for a few hours and have just reset the power options. I’d wager that when I get home this afternoon the screen will still be live. There’s so many hits on Googling that I don’t seem able to find a good search phrase. Does anyone have any tips for me?