For a PC that old, your best bet, since Windows 11 will most likely not work, is finding a light-weight version of Linux to run on it. You can run pretty much any game (as long as the hardware requirement is met) on Linux these days. The two simplest ways on Linux for Windows games is 1. Run it through Steam to use their Proton layer to run the game and/or 2. Use Lutris to run it through wine. It sounds harder than it really is, everything has gotten pretty simple to do on Linux in the last few years and the Steam deck really did change gaming on Linux for the better.
A little off subject: I switched over to full-time usage of Linux since they dropped support of Windows 10. I refuse to allow Windows 11 in my house with all the bullshit they've been pulling. I won't ever look back now. If anyone is thinking of dropping Windows for something else, give Linux Mint a try. It's basically made for people coming from Windows (do not use Ubuntu, they're selling people out like Microsoft).