When I had an HP desktop the motherboard went out just after the warranty was up. So about a year after the purchase.
The buttons would light up, the backlight on the monitor would come on, but otherwise nothing would happen. The sound didn't work either.
Might be the same problem you're having.
I had a lot of photos and work saved on it.
Took it to a repair place hoping that at least they could recover my files but to no avail.
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