Update October 17, 2021 = User reports that the PC is running well after motherboard and daughterboard service setup by DELL-Cares.
I have a Dell Inspiron Desktop 5676 under Dell maintenance (long story) that I cannot keep running under load. Since April of 2007 I and my group have been running the Grid's software.  The Grid is a world wide distributed computing network which works on problems such as  HIV, COVID-19,TB, etc. The 14 computers in my group run 24/7. I was referred to the Dell expert software group which worked the problem for a couple of weeks and declared that it was the Grid's software and returned my $99.00. BTW, I have a second 5676 running this software which has been just fine for over a year.  I think my problem machine may need a new power supply, because I am unable to keep it running even at 30% CPU usage. If I turn on the GPU it immediately shuts down. I am also hearing a rumbling sound occasionally and when I put my hand on the back of the power supply I can feel vibration. (The software allows users to set the CPU usage as well as turn the GPU on or off.) Furthermore, this software is running world wide on millions of computers and there is no evidence that I can find of stoppages like I am having being a problem. I am going to try to get Dell’s attention to take another look at my problem.  Any assistance or ideas any of you can provide would be appreciated.
Inspiron 5676, experiencing unexpected shutdowns