timppu: Or do like me, upgrade the machines with Linux (Mint). :)
darkplanetar: nice, too bad not many games are ported to linux..
If you mean new AAA games, that doesn't really matter as it is old PCs we are talking about. :) So even if I could install Windows 8 on my >10 years old desktop PC, I am pretty sure it still can't run Crysis 3.
As for older Windows games, by the reports many of them are actually easier to get running well under Wine, than under new Windows versions. You never know.
But I don't use Linux/Wine much for that purpose either, that's why I have the retro-PCs running WinXP or Win98SE. But if you still want to go online with the old PCs, Linux is a good option to make them secure internet boxes again, for free.
darkplanetar: you use cinnamon or xfce with your mint?
I currently have Mint running on three different PCs (two of them are old laptops, naturally I don't have that many full desktop PCs lying around). One of them is using xfce, and I think other one is using cinnamon (IIRC). Can't even remember what I selected for the third. :)