Ive got a WD Passport 320GB hard drive that I had formatted on my old dell, where i filled it with about 225 GB of ripped DVDs so i can have my movie library with me wherever i have my laptop. It works really well for that and im happy how well it worked out for that. The problem im having is now that i plug it into my mac and try to drag something into it it says the drive cant be modified. i can take things off of it just fine..and i can play all my Video_TS files just fine in DVD Player, i just cant add anything more to it, which is a bummer cus i still have 70 gigs left to fill. When i look in disk utility at the erase tab it says MS-DOS Fat..which from what ive read only allows you to have 2 gig files, so i dont think its in that format because i have like 7 gig movie files on it. All my other drives work great with my new mac. My Sandisk thumb drive works great and i can add files and take them off, so does my other 320 gig WD drive which i use as my time machine backup. Does anyone have any ideas of what i can do to fix it without having to erase the whole thing, cus i spent a lot of time ripping those DVDs to the drive?