Having trouble with external harddrive

Hey, was wondering if anyone could help me with my hard drive. I'm trying to use it to watch movies on my xbox360. It used to work using the NTFS format, however I reformatted it so that I could use it on PS3's as well since my friends had PS3's I wanted to be able to play it on as well, however once I formatted it as FAT32 it stopped working on my XBOX, so I went and reformatted it as NTFS to work on my Xbox cause that was more useful than only working on PS3's and now it's not working on anything but my computer (which is a mac). Any tips as to why this is happening and what I can do to fix this?