I have a Dell XPS 630i that came loaded with Windows XP. Wake-on-LAN has always worked fine on it; I send the magic packet and the machine comes to life. Since installing Windows 7, however, it stopped working. What could be the problem?
Windows 7 has some more flexible power options (accessible from Control Panel>Power Options), which include per-device settings -- these affect what devices are able to do what when the computer is on, sleeping, or hibernating.
I haven't had this particular issue, but yours could have something to do with these power settings.
The first thing I'd do is the standard advice -- backup the machine, make sure you have the latest BIOS, and make sure you have the latest drivers for the LAN.
If that doesn't help, fiddle with the power settings. Give everything max performance, and if that solves the issue, start scaling back power usage as far as you can go without losing WoL.
Not a solution, but a direction. Good luck.
I had the same problem Optiplex 780, wouldnt wake on lan when windows7 is shutdown.
Solution: Update NIC driver to the newest from dell.
Firstly, I can give hope, Wake-on-Lan works better now I have upgraded to Windows 7.
Secondly, I take this route to the configuration settings.
Control Panel, Network and Internet, Network Adapter. Properties of Your particular NIC, Configure button (Key Point), Power Management.
I also have a look at the Device Manager to see what other devices may, or may not trigger Wake-on-Lan.