WD Passport Essential formally used on PC compatibility issues when using on Macbook Pro

To Anyone That Can Assist,

I purchased a WD Passport Essential 9 months ago (700gb) and used it with my PC.  Recently I transfered all my data onto this HD before buying a Macbook Pro.  I am approaching capacity on my Mac and wish to transfer large files to my WD but it shows up as a Read Only file I can’t drag and drop anything into the drive.  I downloaded the smartware for macs but to no avail.  Am I going to have to format this drive before I can use it on my Mac?  if so, where am I supposed to store the date while I format the drive if I no longer have my PC?  Please advise?

Thank you,

Ian 

Also, 

whenever I click on the smartware it fails to open the application. 

The easiest thing in to find NTFS-G3 on the Apple site and install that. Look at post 2  http://community.wdc.com/t5/External-Drives-for-Mac/WD-drive-as-a-back-up-for-Windows-7-and-MAC-OS-locked-files/m-p/84753#M1830  

Joe