My monitor reactivates itself and displays the desktop for no reason some time after the screensaver terminates and the screen goes black. This has occured with two different keymouse/mouse sets. I changed these to see if it was the source of the problem. I cannot find evidence of anything running in the background and the mouse is not being moved. Where do I look?????

Hi welcome and apologies for delay
What Brand/Model of monitor ? Operating system/Service pack?
Could be the video card driver
the mouse driver... if it' an optical/laser mouse and the sensitivity's cranked up--
if you sneeze near mine it comes on

Dell 19in Ultrasharp Flat Panel Monitor, Dell Optiplex 745, Windows XP PRO SP2, Dell Bluetooth Wireless Keyboard and Mouse.

System is relatively new - 3mos old.

First thing i would look into is any upgraded drivers for wireless keyboard / mouse.
They might be putting out a false movement signal.
I would also suggest looking at Dell's community site for this specific issue

Thanks - I will try both suggestions