In some ways, the downloading of abandonware is as much as moral issue as it is a legal one. I know there are sites where you can easily download hundreds of classic titles, absolutely for free and even with scanned box covers and instruction manuals. However, this is still stealing. Even if no lawyers come after you and no software companies send ‘cease and desist’ letters to the website, it is still not legal unless the original owner of that software has formally released their copyright to the public domain.
As for getting your hands on a retro PC game, there’s always plenty of eBay auctions where people sell old floppy disk games, and usually in lots. You can also check garage sales in your area or look around on Craigslist. You might be surprised what you turn up, plus you’d have the real package instead of just some digital copy. I’m not going to preach right or wrong here, but if you get busted downloading copyrighted software - even if it is decades old - don’t say I didn’t warn you.