Computer Restarts Every 2 Minutes After Fresh Install of Windows 10

Well, we're home and attempting to fix this computer. I made a boot disk with something called UBCD, which is a linux thing, I believe, and has some diagnostic tools on it. I managed to boot the computer using the flash drive, but then when I selected PartedMagic, nothing happened. (It's a black screen that you can scroll up and down on, like old DOS.) When I hit enter, nothing happened. A blinking line at the bottom of the screen just kept right on blinking. I waited a few minutes and still nothing happened. So I shut down the computer.

Then it got very interesting. When the computer booted, it started with one screen, then shifted to another, and then instead of going to windows, it cycled though those first two bootup screens - over and over and over and over. I thought I "broke" the computer! I read somewhere to try unplugging a computer when this kind of thing happens, so I did. A minute later, I plugged it back in and started it up. It started just fine.

But....I can't apparently do any diagnostics on the computer. And we still have the restart any time we're on the internet. Connect to the internet and 1 to 3 minutes later, the computer restarts. Right now it's been on for over 1/2 hour - not connected to the internet and it's fine. But we'd like to use it for more than a lighted paper weight.

I swear, this just gets curiouser and curiouser, as Alice in Wonderland would say.

I would try running it from a full Linux USB flash drive such as Ubuntu. That will let you connect to the internet to tell if it is Windows or hardware.

Okay. I'll try that next. Thank you.

I can't boot from a CD apparently. Flash drive, yes. CD. No. And I did tell the computer to boot from a CD. Didn't matter. So now I'm going to try creating a flash drive with Ubuntu. Unfortunately there, the program (Live Linus) I found for creating a boot flash drive isn't compatible with the latest version of Ubuntu, so apparently I have to download an earlier one. Not sure which one to download. Version 15.04 is compatible, but there are several choices, not sure if it makes any difference:
Ubuntu Vivid Vervet (Unity)
Ubuntu Vivid Vervet (Gnome)
Ubuntu Vivid Vervet (MATE)
Ubuntu Studio DVD
UbuntuKylin (Vivid Vervet)

This is supposedly how to create a bootable Ubuntu USB flash drive. I haven't tried it myself, but getting ready to today.

How to create a bootable USB stick on Windows | Ubuntu

Just tried a couple Linux distros. Here's what I found. Linux Mint seems to be very straightforward to use, connect to the internet and surf with:
Download - Linux Mint

I downloaded the Cinnamon version. I used Rufus to create the USB flash drive with:
Rufus - Create bootable USB drives the easy way

I found that the 32-bit version of Linux Mint Cinnamon will only boot in legacy BIOS (CSM) mode. The 64-bit version will boot in either legacy BIOS (CSM) or UEFI mode. Here were the Rufus settings:

Okay. This is progress - sort of. I *finally* got something to work - sort of. Thank you for that info on creating a flash drive with Mint. It actually booted and I got to a menu giving me an option to work in Mint. Yup. I did. So I selected that. The screen went dark and I was expecting to see Mint. Nope -- computer restarted into Windows again.

So that must mean this is a hardware issue, right? I need to take it in for repairs to find out what the problem hardware is, right? It's not going to matter if I also try Ubuntu now, is it? That thing is still downloading. It keeps stalling. It's not even halfway done.

Btw, I changed the cluster size to 16 kb. That's not the default I get in Rufus. But it worked.

Sure seems like a hardware issue. I think it is most likely the power supply. About the only way to test it at home would be to replace it. A computer repair shop should have a load tester that they could test the power supply with.

Yeah. I've reached the limit of what I can do. Time to take the baby in for repairs. Thanks for all your help.