Luxtorpeda is a clever bit of kit that you can set as a compatibility tool for any game you have on Steam. You just install it, head into the Steam settings for whichever game you want to use it with, ...
Firefox reportedly only ended support for 2001 OS Windows XP (and Windows Vista) in 2023, which means a pretty impressive 19 years of support (accounting for Firefox 1.0 releasing in 2004).
It's truly the perfect home for old hardware.