On The Digital Lifestyle show 303 we talked about some issues a listen had on waking a PC from sleep mode from a Windows Media Center Extender and coincidentally Ed Bott has a great post explaining about some of the wake mode issues in Windows 7.
One of the issues is the PC doesn’t wake if your PC is not in home networking mode (as apposed to wok or public mode) and that in certain circumstances the system can get reset to public mode preventing waking from ARP packet. It well worth reading Ed’s post as it could help you resolve the waking issues
If you’ve ever poked around in the power settings of Windows 7, you’ve probably seen a check box that lets you specify whether Windows should be allowed to wake up when another network device sends it a directed packet.
Today I stumbled across an apparently definitive answer in the Readme file for an Intel network driver:
Power Management and System Wake
Not all systems support every wake setting. There may be BIOS or Operating System settings that need to be enabled for your system to wake up. In particular, this is true for Wake from S5 (also referred to as Wake from power off). Microsoft Windows 7 and Windows Server 2008 R2 do not support on directed packet. Systems with these operating systems will not wake on a ping or other directed packet.
Read the rest on Ed’s blog