XPS 8960, Sleep Mode issue

Read this thread.  Seems XPS 8960 has some odd behavior while sleeping...

Fans got to run so PC doesn't overheat because it's still generating heat.

PSU light is on because it's still getting power from the mains.

Network LEDs blink because it's connected to a network, and potentially waiting for a Wake over LAN packet.  And some apps may be phoning home for updates while PC sleeps.

Other apps like Windows Indexing Service etc might run while it sleeps which could also account for drive access LED flashing...

The whole purpose of the computer going to sleep is to save power. My situation is simply useless to call it, or even have a Sleep Mode in the XPS. Sleep Mode cannot have all these still fully on:

- Front fan
- Rear fan
- Processor fan
- Graphics Card fan (Nvidia 4060 Ti)
- Graphics Card light (Nvidia 4060 Ti)
- Power supply light
- Hard Drive functions light keep flashing
- Network light on the back of the computer keeps flashing.

Three days ago, I realized something else.
When I power down the computer, I can restart it by either left-clicking on the mouse or hitting any key on the keyboard. Is this normal? I don't think so. It cannot be a new thing with the XPS models. Strange. 

That sounds like PC isn't actually shutting down fully, but going to sleep. According to the Service Manual, BIOS has this setting:

At the office  have Precision 3650 Tower and at home I still have Precision 5810 Tower. With both PCs, when they go to sleep, both are literally 'dead'; NOTHING is on or running, which is how I know the traditional computers to behave in Sleep mode. Computers has been so since ever. The Sleep mode also means to conserve power, but the XPS does not. I might as well just leave it on. My Hibernation really goes to sleep, except it wakes up as if it was fully powered off. This XPS style should be called something else.

Have you tried disabling S0 sleep so S3 sleep becomes available? 

The first image at this link shows that S3 isn't available on whatever PC is being used as the test bed, but then it goes on to enable S3 on that same PC using registry hacks.

Worth trying those registry hacks to disable S0 and see if S3 becomes available now?  I'd back up the entire registry and/or image the entire boot drive on external media before making any changes so they can be quickly undone, if the hacks don't help or possibly cause problems.

@RoHe​ 

Got the link. It is quite involved, so I need to take some time. Will surely report back as soon as am done. As soon as am free with the XPS, I'll do at least two registry backups, a system and a disk images of my drive before I use the info in the link.

Thank you so much!