A few thoughts: I, and most computer users are not techs, and don't have testing benches, and don't want to have to service computers. I've been using them for 30 years, Apple 2+, Apple 3, many IBM types including HP, Gateway, eMachines, Compac, and Dell. Service went from long hours waiting on the telephone for technical service to not so long waits when someone half the world away takes control of your computer and usually can't solve the problem without reformatting the HD and never gets it back to factory setups to trying to fix things oneself. Of course, along the way new peripherals were added requiring opening the case and learning about the components. So, I have had a lot of hands-on experience and learning, but little technical background. So, I look to those who do and are willing to share it. The companies aren't interested but most provide space on their websites for forums where volunteers can help their customers. What motivates these people, I don't know, but they do us users a great service. CNET provides such a service, and is the reason I posted here. My experience is that the replies one gets on this site are tech oriented (well, not the one that suggested pulling the plug and replacing it) and often too brief for me to use. I can usually follow directions, but I like to get a cookbook set of steps to follow. I got that solution on the Dell Community Desktop forum. No where did anyone tell me what the flashing yellow light on the motherboard meant nor how to determine what might have caused the failure to power on (whether it might recur - my chief fear) or if it might have been malware. Because I don't know what the various voltages of the PSU mean for failure analysis, I chose to purchase a Digital Tester that shows voltage values of each output connector of the PSU as well as LED lights showing whether it passes some criteria. I know enough to recognize a voltage that is significantly different than its rating, but I do not know what an acceptable range is. So, I let the tester tell me - maybe it does or doesn't do the job. For my limited experience, it did the job, and within the short time it took to plug in about 6 connectors, it gave me a reasonably good assurance that my computer would work. But the fear remains - this is the only PSU failure that I have had in 30 years and maybe 15 computers - that something caused this failure, and I don't yet know what that was. If the multimeter can tell me that, I'd like to know how to perform the test, step by step. I haven't found that information yet, and I don't expect to waste more time (maybe not entirely a waste) researching. I keep hoping that someone will offer advice and point to a solution. But until that happens, I have a computer that works, an undetermined cause, and a yellow LED on the motherboard near the PSU 24 pin connector that flashes when nothing else works. Why?