Check for memory errors with memtest or similar, look for bulging/leaking capacitors, check PSU.

At that age consider retiring it for a newer, more power efficient PC.

Paul.

You know, I would not buy a brand new PC from any store. They are low-price driven for the general public who will just surf, read email, look at videos and do some work once in a while.

You built yours from parts at Tiger Direct. Do it again. You will have a better machine at probably the same cost. There are plenty of users here who can help.

Last year I installed a Thermaltake 600 watt power supply. One would think that should be sufficient. No?

That should be indeed enough unless you forgot to mention some additional GPUs in your first post, this APU has a TDP of 65W, even a 300W PSU would be more than enough. Anyway, if you have one spare laying around, I'd try it (or try this PSU in different computer), even new PSUs can be not completely OK and cause some weird errors. Did the shutdowns start with the previous PSU or after you installed the new one?

Another possibility is overheating, but that should actually not cause shutdowns, just downclocking, but that might also depend on the mainboard.

Anyway, if you decide to buy new hardware, make sure to buy cooler which can easlily keep the CPU/APU well below it's max. temp, the one you have choosen here is obviously not able to cool this APU, specially not for 24/7@100%. Or you need to replace the thermal paste after all those years, I did that recently on my Core2Duo and the fan could spin few hundred (!) RPMs lower to keep same temperature.

Like it was sugested in the thread before, try to run fewer concurrent WUs, so you don't hit the temperature limit and see if the shutdowns stop. That's the easiest thing to try and if they stop, you can start from there and see, when issues arise.

Now the count is 23 tasks computation errors, three valid and one validation pending.

This is not happening with my other projects: Milky Way, Asteroids, Rosetta, Universe. Einstein does cause the computer to shut down for some reason.

But none others are resulting in errors.

I don't have another desktop to test this PSU, but I do have a spare PSU I could put in this one. I'll take out the hard drive, put in an external box and take this machine to the electronics recycling place.

Pretty sure I am gonna build a new computer from parts I am getting specs on.

An AMD Ryzen i7, 32 GB of DDR4s, Mother board, 1TB SSD, 500watt PSU, case, fans.I figure it will cost less than $650 and be at least as good as any costing more than double that.