AHA!! I have fought this battle with many PCs and mostly won. So much so that I have a standard sort of post that I have sent to others on Reddit to try and help them. I will go track down a copy of that from my archive (I don’t use Reddit much) but here’s some suggestions.
First and foremost, you can ask Windows to help you out a bit. There is a command that will tell you the reason why the computer last woke up. The next time it happens, from a CMD window (press and release the Windows key, then type in CMD and press enter) try
powercfg -lastwake Here’s an output from my PC that I am using as I type this:
Wake History Count - 1
Wake History 
Wake Source Count - 1
Wake Source 
Instance Path: PCI\VEN_8086&DEV_9C31&SUBSYS_50041458&REV_04\3&11583659&0&A0
Friendly Name: Intel® USB 3.0 eXtensible Host Controller - 1.0 (Microsoft)
Description: USB xHCI Compliant Host Controller
Manufacturer: Generic USB xHCI Host Controller
That long PCI name can sometimes be decoded by Google if you get something similar and don’t recognize it, or maybe sub-parts may resolve to give you a clue.
While you’re in the CMD window check what devices are armed to wake the PC, here’s output from my PC:
powercfg -devicequery wake_armed
HID Keyboard Device
In any case, the three most common things to wake your PC are:
- mouse (you or your cat bumps it, or vibrations move the table or something)
- wake on lan (yes, even from WiFi, and yes this can be busier/noiser than you’d expect)
- the system/windows “should I do maintenance now” timer
Tackle these one at a time so as to maybe have a chance to know what fixed it.
The mouse is easiest. Go into Device Manager (with elevation to admin), press and release Windows-X and then hold down shift and CTRL as you click on its name, it should prompt for the admin password. It’s important that you do this with admin, or else you WILL NOT be shown the “Power Management” tab that you need. Find your mouse, and right click on it and select properties, then go to the Power Management tab. Uncheck the box “allow this device to wake the computer”
The network should be done similarly. It could be trickier if HP has some special software/driver for it… but you’re looking for “Wake on LAN” although it may have other “branding”.
The windows high precision timer or whatever is a real pain in the a**. Let’s hope you don’t need to fight with this one. I had that on one machine and I fought for weeks to finally find a way to disable it. If you need this option this link may help https://www.howtogeek.com/122954/how-to-prevent-your-computer-from-waking-up-accidentally/ search for “Disable Wake Timers and Scheduled Tasks”.