Hi, I'm a complete newbie and am really lost how external HD work now. I always thought it would be simply just transfer files from any computer and save it in storage, but now I have recently found out that it is not that simple, to use the same external HD on both Windows and Mac Operating Systems. My situation; I have just purchased a Seagate BackUp Plus V1 2TB USB 3.0 and I have an old Seagate GoFlex Desk 1TB USB 2.0, and I know they support both Mac and Windows. First, I'm lost how everything works safely. I thought that 1 external hard drive can share all the files from any OS, since it is just an external. For example, what if I wanted to watch a movie, and the file was originally from a Windows PC, will I be able to play or transfer that easily with or to my MBP? And as well as vice versa, from Mac to Windows? I read about partitions, do I need to partition the hard drive to have Mac only and Windows only in it? If yes, does that mean I must have a duplicate of files on both partitions to be able to play it on both OS? That seems really complicated, I'm just looking for a storage to see all files at once, and copy/paste/move files instantly. I hope you understand me. My old 1TB HD has lots of movies in it, some are also bigger than 4GB, and it has 200GB left in it. I would like to use that with my MBP and also Windows on my MBP. What do I need to do to be able to use that with Mac and Windows on my MBP? Do I have to get rid of the files first inside to set it up for both OS? I have loads of files in it, and was hoping to not have to do that. I have an old Windows desktop PC and I'm planning to get the files in it with my newly purchased 2TB HD, and begone with the ancient PC. I'm also planning to get Windows for my rMBP 15'. So since it is a new hard drive, what do I need to do to set it up for both Mac and Windows use? I also plan to use these externals to watch movies on TVs. But first, how does it work? Can you please help me? Thank you.