NIS stopped Windows 7 from sleeping?

I recently bought another computer and with Windows 7 installed (i don't want Windows 8). It has quite a noisy fan so i thought i would use the sleep mode when not using it. Unfortunately it kept 'waking up' within minutes off being turned off. I searched the internet and there were several possible solutions suggested for what isn't a rare problem.

 

None of them worked, most of them didn't for others either. It had crossed my mind that NIS could be the culprit. It had previously infuriated me on another computer when repeatedly ignoring not to 'perform background tasks when computer is idle' when my computer wasn't idle. Not having used the new computer that much in the month i'd had it i hadn't got around to doing a full scan. I then found the time to run a full scan. Ever since then some two weeks ago the computer has not woken up from sleep mode once unless i wanted it to. So i don't know if NIS had been trying to run whatever the full scan entails on a bit-by-bit basis as in 'running background tasks'?

 

Any thoughts or knowledge as to whether it was indeed NIS causing my new baby's sleep deprivation?