Is there a way to figure out what's preventing my PC from going to sleep?

[AndyD2k]

This worked flawlessly for about 6 months till recently where my system doesn't even attempt to go to sleep. I can't figure it out and even after reformatting / reinstalling (not for this) I still have the same problems. I also tried switching to a different NIC (different manufacturers with different power management options) I was unable to get this going

Anyway, I was wondering if it's possible to see in Event Viewer somewhere the reason why my system never goes to sleep now

 

[volcane]

Too much coffee?

Have you checked if media sharing is enabled? That could prevent your computer from sleeping.

 

[discerning]

What's the OS? If you set the monitor to sleep, does that function correctly?

 

[Motorheader]

Did you upgrade the bios and reset to defaults? If you have done a clean reinstall and it is still happening it could be bios related - S1/S3 states for example. You've changed NIC's but even if different do you have it set to always monitor traffic. You may have a firewall or AV product that is monitoring all processes.

Try sysinternals (part of Microsoft) filemon and autoruns to see what is running at the time it wakes up and enable/disable processes at startup for diagnosing what may be the culprit.

 

[Ketchup]

If it's Windows 7, try turning off the hybrid sleep option.

 

[Ketchup]

Too much coffee?

Nah, probably too much Full Throttle, lol

 

[MobiusPizza]

Sometimes it's not due to software. I know (on some combinations of monitor and GPU) HDMI and Display Port displays have this glitch with handshaking. If the conenction is dropped the display refreshes, and this lead to problems such as PC waking itself back up. E.g. if I sleep using display port, it doesn't work, it wakes itself up when my monitor desyncs. I have ditched DisplayPort and returned to the it-just-works DVI. So much for new tech.

Also check BIOS and play around with the sleep state settings, e.g. enable S3, S1, etc.