Cant Transfer Files

Your drive is probably formatted for Windows.

NTFS (Windows NT File System)

• Read/Write NTFS from native Windows.
• Read only NTFS from native Mac OS X
  [*]To Read/Write/Format NTFS from Mac OS X, here are some alternatives:
  • For Mac OS X 10.4 or later (32 or 64-bit), install Paragon ($19.95) (Best Choice for Lion and Mountain Lion)
  • For Mac OS X 10.5 and later, including Lion, FUSE for OS X
  • For 32-bit Mac OS X, install NTFS-3G for Mac OS X (free) (does not work in 64-bit mode)
  • For 64-bit Snow Leopard, read this: MacFUSE for 64-bit Snow Leopard
  • Some have reported problems using Tuxera (approx $36), which is an enhanced version of NTFS-3G with faster performance.
  • Native NTFS support can be enabled in Snow Leopard and later versions, but is not advisable, due to instability.
• AirPort Extreme (802.11n) and Time Capsule do not support NTFS
• Maximum file size: 16 TB
• Maximum volume size: 256TB
• You can use this format if you routinely share a drive with multiple Windows systems.

 

No, you don't need to buy another drive. Read my post, especially the first 3 bullet points and the bold text. It tells you how to enable writing to your drive.