Yesterday I needed to transfer some files from my laptop to my hard disk and realize that I couldn't because I'm using a MacBook and my external HDD was running on NTFS.
I realized that I haven't install Paragon's NTFS for Mac on this MacBook.
Why do I need to install that? Very simple because Mac OS does not support writing on NTFS(New Technology File System) the same way Windows does not support HFS(Hierarchical File System). You can read the data meaning you can open or copy files from NTFS but you can't write(edit,add files etc).
However both operating systems can read & write on FAT(File Allocation Table).
Things you don't really need to know:
NTFS developed by Windows for Windows
HFS developed by Apple for Apple
FAT for older versions of Windows & MS-DOS
If you'd like to know more about file systems, check these pages on Wikipedia: NTFS HFS FAT32
Why did I format my HDD to NTFS instead of FAT32 since it works on both platforms or HFS since I'm using a MacBook?
1. FAT32 is old and has its limitations. It has a maximum file size of 4GB, so any single file that is larger than 4GB cannot be stored in FAT32. I wouldn't be able to store HD movies or application setup files in it.
2. Not everyone uses a Mac, with HFS, I wouldn't be able to share the files in my HDD with my friends on Windows. Plus, the common TVs with USB port can't read HFS, that means I can't watch HD movies on TVs with my HDD as the input source.
Solution:
Install NTFS for Mac OSX, once you've installed it, you'll be able to read & write seamlessly.
You can get the trial version for free. The full version is priced at $19.95
http://www.paragon-software.com/home/ntfs-mac/download.html
You can also torrent it here (at your own risk):
http://thepiratebay.se/torrent/6403969/Paragon.NTFS.for.Mac.v9.0.1.MacOSX.Incl.Keymaker-CORE
If you don't know how to use torrent, learn here.