So I converted my old Sager NP8760 to a dual boot Win10/Ubuntu 18.4.4 LTS machine on separate SSDs. I had problems initially with Ubuntu where it would not install or when it did I'd have odd video scaling and/or no pointing device/keyboard working. I installed the approved nVidia driver and this fixed the problem. At this point, both Win10 and Ubuntu worked.

Recently, Win 10 and Ubuntu will not boot. The order goes like this.
1. Power on
2. Choose Win10
3. Win load logo
4. Seconds later the machine power off.

Restarting results in the same except maybe Windows attempts a repair before the machine power off. I can not get beyond the Windows logo before it powers down.

The SAME thing happens when I fire up Ubuntu. However, if I start it in Recovery Mode I sometimes can get it to boot when I choose "Resume." Often after I run some of the recovery commands, but don't know if that is why. At any rate, the problem persists. I could be completely wrong, but feel this is again nVidia related.

The machine worked fine as a Win 10 machine. Info below.

17.3-inch 1080p (1920×1080) display with LED backlighting
Intel Core i7 920XM processor
Nvidia GeForce GTX 280M 1GB graphics card
8GB DDR3-1333 RAM

Not enough information to begin troubleshooting.

I can suggest that you try your machine with live media to see if your hardware is still functional. For all we know your hardware is dying.

Unstable power and failing RAM can cause these symptoms. Run a long test of RAM to both check RAM as well as see if the PC can stay powered up without running a normal OS. If the PC is out of warranty, take off the cover and inspect for obvious trouble. Leaking and/or bulging capacitors cause power issues. In recent years this has been uncommon on motherboards and graphics cards, but has remained common inside power supplies. A GTX 280 is over a decade old, so it too could have one or more failing or failed caps. If this is a laptop, it's probably time to retire it, unless different or reseating RAM seems to solve the problem.

I second mrmazda's suggestions. It definitely sounds like a hardware issue.

It is an old machine that I've upgraded over the years. Vista>Win7>win10, SSDs. I bought it Jan 1 2010. However, it worked fine until I made it Dual-boot two months ago. I don't know how to run a "long test of RAM". Is that the Memtest option in GRUB?

I do suspect the video card, In the previous year I had very occasional blue screens that seemed to fault the VC. I'd love to try a replacement, but they're still to expensive (used) for a throwaway machine.

Long simply means mulitple passes, time based rather than pass based. Overnight is generally quite sufficient.

Guaranteed working used ones can be had for very little money from eBay.

Running "memtest86+ Serial console 115200" now. Assuming that's what we're talking about?

Unfortunately, those VCards are for desktops. Laptop versions are going for $100. Somebody selling one from my computer model lists theirs for the crazy $299.99!
I wish I knew which other models could work with this machine.

https://www.ebay.com/sch/i.html?_fro...+Card&_sacat=0

If your video card is on the last leg you can try running it with a software framebuffer like fbdev or something like that if you want to continue to use dead hardware. Otherwise it's not a Linux question anyway.

Is the fan fully operational? Not spinning could cause the BIOS to initiate a delayed poweroff instead of during POST.

Is any part of the cooling path blocked by 14 years of accumulated dust? That could have caused irrecoverable damage.

Possibly the GPU module has one or more failed ($1.00US or less) capacitors that could be replaced with a modest amount of soldering skill.

You need to check if coolers work. Problem with both Linux and Windows means very rather a hardware issue.

I knew at least 2 cases with cooler problems that made the computer to stop after some time on. The first one was my sister's desktop, where the graphics card's cooler was off. The computer stopped after a time varying from seconds (or half a minute) to say 10 or 20 minutes.
Another case was a windows Vaio laptop that stopped after about 30-40 seconds (boot up wasn't complete). It suffered a severe mechanical shock (fall). Repeating boot attempts made it stop after a shorter time, 6-10 seconds. It seems that processor's ventilator was dead, and for the 2nd or 3rd boot try the chip was already warm by the previous attempts so it went down sooner.