monitor unable to go to sleep

I am trying to enable the monitor to turn off. It's a new computer and when I

first had it it would do it fine. I did have some trouble with automatic

updates, it got stuck trying to download one of them and kept asking to

download again and again. Got it sorted with a Microsoft tech guy who

suggested download and running winupsecureWinXP.bat.

This may have nothing at all to do with anything but I thought it might be

worth mentioning.

My monitors are two Philips LCD.

The monitors will go off and stay off for about one or two seconds then come

back on again. If I reboot and go to the welcome screen and leave things,

then the monitors will switch off as they should. Something must be

continually running and waking them up. Any ideas?