I’ve written before about how Vista’s new power management sucks. Since then I’ve found that getting it to go to sleep (even with the modifications to the advanced settings) is a bit flakey at the best of times. I think I’ve tracked it down to uTorrent – if it’s running (or even has been running) then Vista will refuse to go to sleep.
So, assuming that I even get it to go to sleep I’ve been finding that Vsta is waking itself up at 4am each night (and not going back to sleep even though the inactivity timeout is set to 1 hour). I’ve eventually tracked this down to Media Centre’s automatic listings update feature. Turn this off and it won’t wake itself up – not a great workaround for those that use it a lot :(