old pcs are fun if you use old software on it, it really hits that spot many pursue, the magic goes out soon, but it does feel like 2008 for a brief moment again.
my windows xp was wonderful in loading internet explorer (it took less than 10 seconds to load a page), but it sucked to load even the most simple cereal box games.
thats the things you will usually find on those:
personal documents, from school or work.
old images, usually family photos that the owner transferred from his 2000's nikon camera.
old songs.
a cd burner.
clocks, a lot of clocks and maybe some calendars.
one or two games other than windows experimental ones (solitaire).
about donating them, eh "old tech" from 2000's are not rare, I worked at this IT company for some time and they MOSTLY had 1995-2005 PC's. now if you find a macintosh in working order... sir... you have struck gold.
"I worked at this IT company for a time and they MOSTLY had 1995-2005 PC's"
it was so many that they started giving away some, because we didnt have space anymore, for some time my only work was to rip old 60GB HDD's the entire day (we had towers and towers of those).