[SOLVED] Windows 7 will not go to sleep

Windows 7 will not go to sleep using timer set in Control Panel. I can put it to sleep manually. The monitor will shut down properly based on the timer setting, the the PC just keeps on running. Latest driver updates are in place, and Control Panel settings have been checked and rechecked.

If you've already updated the graphics and chipset drivers and that didn't help, then it could potentially be a USB device or perhaps even a running application preventing the system from shutting down.

By Timer in the Control Panel, you mean through the power options , or?
In the Power options, check you have these settings:

The Hard disk
Set to a sort time before the computer is set to sleep.

Sleep after
Set to a minimum (1 minute ), after Hard disk and Display is set to turn off.

Allow hybrid sleep
Off.

Hibernate after
Never.

USB selective suspend setting
Disabled.

In Power buttons and lid
Start menu power button
Sleep.

PCI ExpressLink State Power Management
Off.

Turn off display after
Set to a minimum of 1 minute before the computer is set to sleep.

Multimedia settings
(When sharing media)
Set to Allow the computer to sleep.

If you are having sleep mode problems and using USB mouse and keyboard, you should read the following KB article and its associated articles:
http://support.microsoft.com/kb/266283

I was having problems coming out of sleep mode...made the suggested changes to the registry and the problems went away.

However, my problem was a little different. Caused by a faulty PSU...installed new PSU and the coming out of sleep mode problem was gone.