Do you have old OS'es just for nostalgia?

Solution
Nope.
7 & 8.1 in VM's, just for testing purposes.
Vista and XP? Not enough time to mess with those.

I do have a very old laptop with Win2000 still installed. It is used once or twice a year to interface with the OBDII in my truck.
Why? Because that laptop is the only one here with a serial port.
Yes, I could buy a fancy new bluetooth, WiFi, or USB OBDII adapter. But this one works as is. Why spend the extra money to replace something that works.

That reminds me...I should crank it up on the truck this weekend.
Nope.
7 & 8.1 in VM's, just for testing purposes.
Vista and XP? Not enough time to mess with those.

I do have a very old laptop with Win2000 still installed. It is used once or twice a year to interface with the OBDII in my truck.
Why? Because that laptop is the only one here with a serial port.
Yes, I could buy a fancy new bluetooth, WiFi, or USB OBDII adapter. But this one works as is. Why spend the extra money to replace something that works.

That reminds me...I should crank it up on the truck this weekend.
 
Solution
No need to waste time reinstalling it. Convert your old OS into a virtual machine prior to upgrading to a new computer/OS. Then in the future you can run it in a window on a modern computer any time you feel like it.

https://www.vmware.com/products/converter.html

I have copies of my old Win98 and WinXP machines saved this way (the Win98 was a straight VM install that I loaded my old software onto, not a conversion). The only old OS I keep around on its original hardware is an HP 200LX palmtop with DOS 5.0 and a copy of Ultima III on a 5 MB PCMCIA flash drive. (I paid $110 for that flash drive in 1997, all you people who complain about SSD prices being stuck at 30 cents/GB.)