External HD bizzare problem

Hi there first time posting and in desperate need of help

This is a strange one, my macbook hard drive recently died and I had to get a new one from apple, as annoying as this was its ok cause I back up onto an external (seagate). While the mac was out of use I tried to watch some movies on my hard drive via a PC, it recognised it but wouldn't show it so I tried to make it work on a PC by giving it a driver name (or something). I noticed that the word "Formatting" appeared and I panicked and unplugged. Worried for my lost data I checked it on my xbox 360 (it has always work on there no problem) and everything was there and working so I though "Thank god"

But!

When I got my mac back I tried plugging it in and it wasn't appearing on the desktop, when i ran disk utility it knows it is there but wont let me verify or repair the disk. I know if it goes onto a PC again it will try to format it. I have tried disk warrior and disk repair but they aren't seeing it when I run them. I know the info is there and I literally cant lose it so I turn to the people on this forum and hope you can help me.

someone must know a way of getting it to work?

Thanks x