The title pretty much says it all. A couple years ago or so I put Windows 8.1 onto a Mac because it was on laptop I didn't use anymore and I was experimenting. I also didn't just put it on a partition or anything. I fully formatted the laptop with Windows so now that's all it has. Now though I really want it back to Mac OS, but no matter what I've tried I can't seem to get it to work. It's been a while since I tried to get it to work so I can't say 100% all of what I tried. Any extra bit of information I could offer is that it's a 2012 Macbook Pro and I have a software install disk for an old version of Mac OS (snow leopard I think).
If you rewrote the disk with Windows 8.1 and formatted everything, there is no chance of getting your Mac OS back. I assume you've tried to reinstall the Mac OS from your disk (bootable I presume, not just a repair disk). I don't know exactly what you mean by "I can't seem to get it to work." How far in the process have you gone before it did not work?