2-3 PCs unused...What to do with them?

[Antistatic12]

As a few have said Folding@home, or you could try BOINC.
You could also just setup NiceHash.

 

[Moonzy]

1 hour ago, Antistatic12 said:

You could also just setup NiceHash.

His spare rigs most likely will spend more on electricity cost than income

 

Still think giving it to people in need is nice, especially during covid when everyone is stuck at home and some people needs to study/work from home

[Bombastinator]

Computer one is absolutely a viable office work machine.  Donate it to someone who has no computer? Sell it? The second one is viable for quite light light office work and would be functional as a HTPC of its quiet enough.  It will still surf the web and play movies.  Freegeek would take it if you have one in your area.  They’re rare these days though.  The third computer will actually game if it takes a decent overclock, though perhaps not for very much longer.  That one might still be worth some money though you’d want to dump it fast. 
 

if you don’t want to sell or donate anything, all three could do router or NAS duties, and the quietest one could act as an HTPC to play movies on. The oldest of the three may have graduated to Linux, which means router and NAS duties are probably where it might want to go.  It also seems to have the most sentimental value, so it can pull its weight into its dotage as an appliance system. 

Edited January 24, 2021 by Bombastinator