XP will not remain in Standby

I have my computer set so only the keyboard will bring it out of Standby but now it no longer remains in Standby. Nothing has changed on the computer.

As a test I set the power options for Monitor, Hard Drive, and Standby for 10 minutes. After 10 minutes it goes into Standby but 10 minutes later it powers back up but the monitor does not come on. It continues this 20 minute on - off cycle unless I shut down. I have no Scheduled Tasks at all and no Start Up programs that would cause this.

Any ideas?

 

The log returned:
EnumProcess
Windows firewall is off
No known processes detected

I have also detached everything from the computer - printer, DSL, mouse, and the standby problem remains.

 

Are you connected to a network? My PC would wake every time the network connection was checked.
I fixed this but don't remember the steps at the moment.

 

I am not connected to a network.