Love how people and bots are still replying to a 3 year old thread, but this forum is so ghostly nowdays.
Anyway, I've got a real winner here.
Its 2016, and at my workplace is a trio of machines running MSDOS 6.22.
That's right, 25 year old software. On 25 year old hardware.
The hardware for each machine is an i386SX at 25MHz, with 640kb of 30 pin simm ram in it.
When I started working here, they were without hard drives and booted from 3.5" floppy discs. Over time the floppy drives began to fail, and I figured out that I could use a 2GB industrial CF card as an IDE hard drive. Was just a matter of finding valid CHS geometry for the bios to understand how to get to the data.
Each unit serves as a 2 axis precision CNC controller, making use of an ISA servo card and proprietary software to do so. There is absolutely no reason to upgrade these units any further, and they will serve in this function until they die of hardware failure. Given that I can find museum quality mainboards and RAM to fit them on ebay, I can probably nurse them along for another 10-20 years without issue as long as the servocard does not malfunction.