HDD Unrecognized

[jpga13]

I had an external drive plugged into a mac mini with some of my movies and tv shows. I took the drive and plugged into a windows laptop to add some files but the windows machine didn't see the drive and I just took it back to my office. Today i tried to plug it back into the mac mini and it says the drive isn't readable and did I want to Initialize, Ignore, or Eject. Disk Utility say the drive but it was greyed out. I tried it back on the windows machine and it didn't recognize it in windows explorer but it did see it in Drive Management and said it had 200mb EFI partition that was healthy, a 250GB Primary that was healthy, and 128mb unallocated.

Any suggestions on how to revive this drive or recover my files. The drive is working fine but something must be corrupted.

Thanks!