The disk was not repairable...

Okay so I have a 13 inch macbook I bought last Christmas. Ever since 1-2 weeks ago, ever since I plug in my WD Passport 500gb external HD, I get this message:

The disc "WD Passport" was not repairable by this computer. It is being made available to you with limited functionality. You must back up your data and reformat the disc as soon as possible.

from what I see... I have to clean out the entire disk and wipe it out? I have 250GB of tv shows and movies that I really don't want to go out and look for... and my macbook doesnt have the HD space to hold it. I can't add file to the external from my macbook and I can't create folders or do anything of the sort... I can open files though.

On the other hand, it seems to work fine on my PC. I can create folders and add files just fine and it's all perfect.

What should I do?

In your situation I'd be buying another hard drive, they are not expensive. You don't need an enclosure for it at this stage, simply a USB2-SATA adaptor kit. Transfer the contents of the problematic WD external drive to the backup drive, and then reformat the WD, providing it is in sound order.

As an alternative, you could have that task done by your nearest computer service technician, using a 'meantime' backup drive. Whether or not that would be cheaper than doing the job yourself I can't say.

Alright thanks for the advice. Would you have any clue as to why it's only messing up on my Macbook and not my PC?

Assuming the ext WD was working okay with your Mac, and doing what you said you were trying to do when the problems started, ie. "add file to the external from my macbook and I can't create folders or do anything of the sort... I can open files though", there may have been some damage to the file structure and/or some sectors of the physical disk.

If however the problem is something 'new', and the event you described was a first time occurrence, then it's probably as a result of incompatible disk formatting, ie. the WD is formatted NTFS, which will not work with Mac. You can ascertain what the WD format currently is if you mount it to your Mac and then use Disk Utility to get info about it.

When reformatting the WD, use MS-DOS to make it compatible with both the Mac and the Win PC. If however you wish to use the WD with the Mac ONLY, then reformat it HFS (Mac-specific).

Okay thanks for the advice. I know for a fact that it is indeed FAT32 (I can't fit single files greater than 4GB on it). Using MS-DOS to reformat -> Using the Command Prompt (Start>Run) on Windows?