Energy Saver has suddenly stopped working

Reading the support article led me to use Intego Virus Barrier to check my Western Digital HD to which Time Machine backs up. It showed some issues. I now want to delete old backups for a 6-months period. I moved them to the trash on the iMac but can't find a way to (Secure) Empty the Trash. I shall post this as a separate problem. I am reluctant to try the two other options in the support article in case I lack sufficient skill?

Before your reply arrived I had already solved the Trash problem by putting the files back on the WD disk and halving the quantity I put in Trash. It worked. So I think it was an indigestion problem by giving it too much to do at the same time?!

However, I am still suffering from problems with Energy Saver, which is behaving erratically. I have run Disk Utility and a complete scan of both my HD and my backup drive with Intego Virus Barrier. I am now trying to find time to understand Activity Monitor because when I get up in the night I now often find the iMac wide awake, though I left it sleeping when I went to bed, and my external drive flashing with activity. I have tried turning Time Machine off but I don't think that helps. I am worried my computer may have somehow been entrapped by an evil external force. Help!

Thanks, but I am paranoid about security. I've had Intego since 2009 and have just paid for a further year's extension. Over all this time it has never caused a problem so I can't believe that it is the cause. Indeed, I've tried turning it off (as also Time Machine). Way back in 2009 I suspected a conflict between the two but since then they have coexisted happily.

Reading up about Activity Monitor hasn't helped.

Problem solved! My most recent scan of the WD external hard drive by WD Utilities still showed all tests passed but then later on kept pestering me with warnings about RAID configuration issues, to which I could find no solution. So I have disconnected it prior to getting a replacement (some other make! - this is the second WD drive that has failed after only a year) and everything is back to normal. It had even affected the time it took to open System Preferences (which I was doing a lot, fiddling about with Energy Saver, Time Machine and Activity Monitor).

So thank you so much for your time and trouble. I certainly now know more about Energy Saver than about anything else on my Mac!