Computer will offten turn back on when in sleep mode

Hi i have been experiencing this problem since i first built my PC. It seems to wake up from sleep at random times in the nite(very disturbing). I have already turned off all the devices that wake it up that are not USb interface and I have no idea how to proceed to trouble shoot this issue, please help if you can.
Thank you,
J
EDIT: It goes back to sleep on its own(sometimes)

have you turned off the waking from lan of your network card? also, there are some power management settings in bios which deal with auto waking up from sleep. see if this is the case, as windows settings might be over-ridden by bios.

problemshredder said:

have you turned off the waking from lan of your network card? also, there are some power management settings in bios which deal with auto waking up from sleep. see if this is the case, as windows settings might be over-ridden by bios.

Alright i turned off "Shutdown On-Lan" property of the network card. I do not know if that has solved the problem will post if it is.Thanks.