Desktop powers on for few seconds then off.

[MARKBB]

Was attempting HP hardware+software update. After several minutes of not powering back on I hit power button. Now it just cycles on+off.  

[Prométhée]

Hello

[start]
This is an automatic response
in order to avoid writing the same thing each time

Some elements may therefore not apply to you 
To be able to answer you effectively, we need some information

we need the exact model of your computer, and the product number
To find it follow this
for a desktop computer

HP Desktop PCs - How Do I Find My Model Number or Product Number? | HP® Customer Support
and for a laptop
HP Notebook PCs - How Do I Find My Product Name or Number? | HP® Customer Support

Give the full name with the product number P / N

this is not a model:
HP Desktop M01-F1xxx
the requested product number must look like this
Product Number: 9EE50AA # ABA
the model corresponding to this number will therefore be
HP Desktop - M01-F1033wb

Give the full version of windows

for windows 10 type winver in the search box
if you give the best information
your problem could have a solution more quickly (depending on the difficulty, of course)
Learn how to use the Community

Advice for asking the "Very Best Question"

First-Time-Here-Learn-How-to-Post-and-More

[MARKBB]

Copied verbatim from the label on the bottom:

Model name:

HP Pav 590-p0016 DT PC US

Model number:

3LC18AA#ABA

Follow-up:

I plugged in a spare HD (a fraction of original 1TB) I had laying around + at least got the power to stay on, but that was it.  

[Prométhée]

"Was attempting HP hardware+software update "

tell me what you did, and replaced exactly?
if you put everything back, the computer starts up or not?

[MARKBB]

I went the HP support site for a comparatively minor issue. After site locked into my computer, I figured the hardware + software updates couldn't hurt - might help - since I hadn't been to the site in a while. I took all that was offered/available followed all the prompts to the restart stage. After several minutes of no activity I hit the start button.

It cycles on + off ever since. Putting a different HD in, the power at least remains on. My OS is Windows 10. 

[Prométhée · Accepted solution]

If you restart, and press f10 several times, do you have the bios menu?

[MARKBB]

I'll try that when I get a chance. Thanks.

[MARKBB]

Well I decided to drop what I was doing as the suspense was killing me to try this - to try ANYTHING. To top it all off the original issue that led me to the Support site in the 1st place has been resolved as well. I can't thank you enough for what may have been an obvious, simple suggestion to you, but I had no clue. 

I'd already spent a few hours exploring options like 1) a refurbished computer; 2) replacement HD to attempt a do-over ( I would've had to drop an extra $90 for new Windows 10 since refurbished desktop came pre-installed).

So THANK YOU so much for your generous assistance. If there is any appropriate way to further express my gratitude, I'm open for suggestions.    

[Prométhée]

Well I don't know if I understand your message correctly.
But, it's done
"THANK YOU so much for your generous assistance. If there is any appropriate way to further express my gratitude, I'm open for suggestions."
Thank you, it is more than enough, this little sentence touches me a lot, what more could I ask for!