WD Elements 1TB is "Read Only"

I recently purchased a WD external 1TB hard drive from target. The sales associate assured me several times that the device would work on MAC and PC out of the box (Target’s fault not WD). I took the device home and downloaded some footage from my PC expecting to be able to pull it up on my MAC laptop, which did work, but when I tried to put new footage from the MAC on the hard drive, I got the message that the hd ws “Read Only”. So I decided to visit the Western Digital website and see what was up. I found the tutorial for reformating the hard drive for use with both MACs and PCs, but I am ot very tech savvy, and I’m concerned about the risks. If the situation were reversed, and my PC could only read the files and copy them, it wouldn’t be a big deal, but I need to be able to store things from my MAC laptop to the hard drive. If anyone has any advice I’d greatly appreciate it.

Is your WD Elements formatted with a Microsoft NTFS file system? AIUI, Mac OSX is able to read, but not write to, NTFS volumes, at least not out of the box.

Here is an open source NTFS driver for Mac OSX:
http://www.tuxera.com/community/ntfs-3g-download/ http://macntfs-3g.blogspot.com/ http://en.wikipedia.org/wiki/NTFS-3G

Here is a commercial product (Paragon NTFS for Mac OS X 8.0):

However, you may like to read this thread:

Guide: Enable native NTFS Read/Write in Snow Leopard: