I recently bought one of these, just before the $100 discount started:

https://www.costco.com/Dell-Inspiron-Desktop---Intel-Core-i7---2GB-NVIDIA-Graphics.product.100344519.html

I think they'll give me the $100.  But, anyway, the reason I'm writing
to the list is that I've had some peculiar problems and I'm wondering
if I have a bad computer or one that has some kind of incompatibility
with Ubuntu.

Installation of Ubuntu 17.04 was a breeze.  I kept the Windows 10 in a
100 GB partition.  I started copying files from a USB 3.0 external
drive, but sometime after the screen blanked I tried to enter my
password at the login window and the system just hung -- it never
accepted the password, the screen froze, it seemed to take no input
from the keyboard and while the mouse cursor moved on the screen,
clicking had no effect.

Often when I press the power button, it comes on for about a second
and then turns off.  I saw that happen once after powering off -- it
turned on for a second, then off again.  That seems odd.

I had to start in recovery mode.  That seemed to fix it, but the next
time I used it, it got stuck again and I had to use the power button
to shut it off.

Does this sound like bad hardware?  Or could it be some kind of driver issue?

I'm also wondering what is the easiest way to get the old memtest86+.
Didn't it used to be in the Ubuntu ISO?  I thought it was there.  I
would have run it already if it was easily accessible.

Thanks in advance.

Mike