hello , i am a first time mac owner for about 3 weeks so i don't know much for OS X . i have two computers, a 2012 Macbook Air and a desktop with Windows 7. I am moving in Sweden for a Masters Programme and i want to buy and External Hard Drive. I have heard that the hard drive will not work with OS X and windows 7 at the same time due to different format. Is there a way to make the Ex HDD usable for both systems or i will have to select with which i want to use ?