EDIT 03/16/2019: I am updating this review (again) going from 1 star to 5 stars! After reaching out to SJ Computers, I spoke with a very helpful tech who did further troubleshooting of the power supply and concluded it failed. He then shipped out a new replacement power supply with 2 day delivery at no charge to me! Just finished installing the PSU and now I'm back in action! A BIG THANK YOU TO SJ COMPUTERS for your awesome support and help! Now THAT is exceptional customer service!EDIT: 5/30/2019: Replaced the DVD Rom drive that came with this computer with a CD/DVD/RW drive from my old computer and the 160GB drive with the 640GB drive from my old system. Putting Windows 10 on it was real easy now that Windows allows you to make a recovery drive on a USB flash stick. This system is real easy to replace components.Anybody can do it.Original Review below:Received the Dell Optiplex 780 computer today. It was very well packed and when I took it out of the box, I inspected the insides and it looked like it came fresh off the assembly line. Nice refurbishing job. Shipping was fast too.Powering it up for the first time, it took Windows 10 a LONG time to boot. But, that happens with any fresh install of Windows. It takes forever the first time you start it. After that, it doesn't take long at all to start. I expected that.Activating Windows 10 was pretty easy too, except trying to read the SMALL string of numbers and letters on the case sticker you need to enter during the activation process. I also expected that. But activation was a snap.Once I got the niceties of starting the computer for the first time and activating Windows 10, I got to see how it handles. It's a pretty speedy machine. Overall, much faster than the aging Acer Aspire that I am replacing this unit with. Seems very stable so far. And adding my external hard drive, webcam, and other accessories to the USB ports were a breeze. Overall, this is a great machine for the money.But, why not 5 stars instead of 4, you may ask? I'll tell you.1st, the advertisement is for an Intel Core 2 Duo 2.9GHz Processor. When I checked the hardware, it was actually an Intel Core Quad CPU 2.66GHz Processor. Not a deal breaker, and no big deal to me, but I expect to have the CPU advertised, and not a slower one. That in of itself would not have knocked the star off the raiting.But the big thing that did was the CD/DVD drive. When I went to install the WIFI dongle, I had to install the drivers from the included CD. Fair enough. But, when I pushed the button to open the CD drive, the door was jammed! It was only after several atteempts that I gave it a thump with my hand, that it finally opened. And opening/closing it shows it jams more often than opening on it's own without a a thump to the case. If this system is 100% "refurbished", then someone screwed the pooch royally during QA testing. That drive should have been rejected during refurbishing outright.Now, I'm NOT saying don't buy this system. Outside of those two quirks, this is a very capable machine and Windows 10 runs smooth and quick, and overall setup is a breeze. Had this machine been given a 2.9 GHz processor and not a 2.6 GHZ, and not had the intermediate jamming of the CD/DVD drive door, this would have easily rated a 5 stars with me.Would I buy this machine again? Sure. But next time, I'll choose another seller who'll make sure the CPU is at advertised speed and with a CD/DVD door that doesn't jam.