Mike can't get his computer to go into power saving mode. Leo says it could be a bad install and recommends installing from scratch, rather then upgrading. It may also be that Windows Installer doesn't see that his computer supports ACPI. Sometimes the installer gets it wrong and doesn't install the feature. There's not much he can do besides reinstalling Windows. He has to be sure to install the right kernel, and that's the problem because it's automatic.
Mike should look in the BIOS setup to be sure that ACPI is enabled and configured. Also, he should turn off "Wake on LAN" in the BIOS as well. The mouse or keyboard may also be generating stray signals or there may be something running in the background. He should try using AutoRuns by Microsoft and it'll tell him if there's anything running in the background.