PC won't stay in sleep mode

[diadara]

As the title says, my computer won't sleep. It will randomly start after being put into sleep mode, sometimes several times at night.
Here's what I've done:
Turned off Wake on LAN
Turned off mouse wake function
Turned off keyboard wake function
Turned off Windows automatic updates
Checked the logbook for latest activity, it hasn't registered anything
Checked cmd for latest wakeup, hasn't registered anything

I am at a loss. I see no other choice but to reinstall or maybe remove the CMOS battery and reset BIOS?

 

[Chintan Gohel]

any process that runs in the background such as a virus scan?

 

[diadara]

any process that runs in the background such as a virus scan?

No only Microsoft Essentials

 

[Chintan Gohel]

No only Microsoft Essentials

what about hibernate? Does it work okay?