Check
this out.
Take your pick.. I never really played too many dos games. Only some like Sopwith, Wolfenstein, Doom, Dinopark, and maybe a few others but they were all fun at the time.
I even went back a few months ago to dl some old dos games and play them with DOSBox, to remember the good 'ol days and see if they are still as fun as they were before. I ended up downloading over 2GB of dos games and was still browsing more.
You can also visit
this site to try and find more games, they have
almost anything you can think of and more.
Sometimes it's fun to go back and see how most games started, ever played the first GTA? GTA1 and GTA2 are now freely available and can still be quite enjoyable if you have nothing better to do.
You can also try to dl a NES emulator and some roms to play that instead, maybe even SNES too if your older PC has at least 200MHz processor, 32MB RAM, and DX6/OpenGL. If you find the right place you can easily get 1000s of roms that barely take up any space.
Over 4000 NES roms don't even take up 500MB but almost 4000 SNES roms take up a little over 3GB so not sure how much you can hold altogether.