For the past couple of weeks, my iMac (a mid-2007 24" model) has been acting weirdly - getting a lot of beachballs (especially when using iTunes), and it intermitently freezes, with non-responsive UI ...
A friend was recently given a 2019 iMac, apparently as a gift. Turns out it was actually a 2007. My friend needs an appropriate OS. I still have snow leopard on my 2007. What OS will work on her 2007 ...