Something weird is happening. my samsung External HD formatted in NT works perfectly (read and write) with my macbook pro, but on my macbook air I can only read. Can I change the permissions somehow or do I have to reformat everything?
Overview of the four major file systems (called "Formats" in Mac OS X) used on Windows and Mac OS X, compiled by GGJstudios. You can use Disk Utility to format any HDD to your liking.
Any external hard drive will work with PCs or Macs, as long as the connectors are there (Firewire, USB, etc.) It doesn't matter how the drive is formatted out of the box, since you can re-format any way you like. Formatting can be done with the Mac OS X Disk Utility, found in the /Applications/Utilities folder. Here are your formatting options:
HFS+ (Hierarchical File System, a.k.a. Mac OS Extended (Journaled) Don't use case-sensitive)
You can use this format if you only use the drive with Mac OS X, or use it for backups of your Mac OS X internal drive, or if you only share it with one Windows PC (with MacDrive installed on the PC)
Open System Preferences and the last row or section on the bottom (called OTHER) and see if Pagaron or NTFS-3G or something else is listed there. If there are several things listed there, check them all and the one responsible for writing to NTFS volumes will be quite apparent.