2 areas to look at.
1. Go through the BIOS and verify the sleep settings (my apologies if this is a bit vague but BIOS settings vary from PC to PC)
2. As for the NIC, go to the Device Manager and check the Power Managment under the network cards properties. There should be a setting “Allow this device to wake the computer”. I usually enable (checked) this setting.
I think there is a guide that Babgvant put together about computer sleep settings.
