Where should one find/get retro pc games from?

It annoys me how most dvd/cd games came with a code or you have to pay a crazy amount for retro titles. im looking for game si can test on a 32 bit, 2gb of ram pc or even turn it into a retro gaming machine. i have a bunch of blank dvd’s laying around so should i put some on a dvd by chance. where do i even find retro games...