Same thing happened to me once, my laptop woke at 3 AM, music blasting and all

. I traced it to Windows Update, which was set on full auto at 3AM.
If you want to turn if off:
- Start>Run open: gpedit.msc
- The Local Group Policy editor will open.
- In the tree list on the left select:
- Local Computer Policy
> Computer Configuration
>> Administrative templates
>>> Windows Components
>>>> Windows Update
- In the panel on the right, double-click on :
- "Enabling Windows Update Power Manager to automatically wake up the system to install scheduled updates" (pfew...)
- Select the 'Disabled' option.
Or, you can just change the Time setting in Windows Update.
Hope this helps!