Hi, I recently bought an imac and very happy with it so far. Having been on windows before, I backuped up a lot of media on to my hard disk. A problem I have is,that I can't add things to my external USB hard drive with Leopard although I can only read from it. Is there away around this? In future,if i Need want to buy a new hard drive,is there a particular format that reads well with both OSX and Windows?