I recently got a macbook air and I'm trying to make my external HDD to work with it. OSX supports reading from NTFS but unfortunately it doesn't allow writing. I need my files to be accessible on any Windows machine so I can't simply format it to HFS+. I know you can enable write support manually but Apple disabled this because it seems to be unstable, as are the third-party alternative as you can find user complaining all over the internet.
I'd rather dodge the problem using a filesystem that's fully supported on both Windows and OSX and go for exFAT (aka FAT64). My problem is I don't want to loose the files that are already on my HDD on the unique NTFS partition. What I want to do is create another partition using the remaining space of the HDD, format it to exFAT and then transfer all my files before formatting the NFTS to exFAT and merge it to get only one big exFAT partition containing everything. I've already done something similar using GParted but it seems it doesn't support exFAT due to patents on exFAT (thank you for that Microsoft.).
Do you know any software that would do the trick? It can come either as a liveCD or as an OSX software.