A computer will only sleep or hibernate if it is allowed to do so, and the biggest single cause of not being allowed is this.
For reasons only known to Windows and Microsoft, the default setting for ‘Wake on LAN’ and ‘Power Management’ is ON.
So, as soon as the computer detects the passage of data through Ethernet or Wi-Fi, Windows springs into life. It’s like the scenario where a smartphone rings and everybody within earshot grabs their own phone.. 🙂
How to fix it..
OK, ready? Control Panel > Network and Sharing > Change Adapter Settings.
Now right click on the connection being used > Properties > Power Management tab > uncheck the boxes starting with the lowest box first.
OK.. job done..