The Dell Optiplex 9010 acting as a file server woke up dead after I plugged it in after returning from a road trip. Its ID sticker shows a manufacturing date almost exactly nine years ago and the problem was exactly what you might expect:
I’d never measured 100 mV on a CR2032 before.
Because the Optiplex runs headless in the basement, diagnosis required hauling it upstairs, booting it with a display & keyboard, whacking the date into the current decade, then resetting a few other vital bits.
The electrolytic caps looked to be in fine shape, though.
The Smell of Molten Projects in the Morning 
I think it’s time to replace the battery on the house Optiplex. When it’s powered down for a minute or two, the internal clock goes off by 15 seconds. I’ll take that as a red flag.
At least it’s easier to deal with than the Inspiron it replaced…
Admittedly, the CR2032 I installed is only a few years younger than the Optiplex. It’s been sleeping all that time, rather than being hard at work, so it’ll likely outlast the chassis.