Your external drive is more than likely formatted NTFS, the Windows NT format, which Mac OS X can READ but can not Write to.
You have a couple of choices.
1) Return the Mac, you have 14 days from date of purchase to return the Mac for a full refund, and stick with Windows
2) Get an Add-On app for the Mac that allows OS X to both Read and Write to a NTFS formatted drives.
3) Get another external drive and format it in the Mac format then Copy your images off the Windows NTFS formatted drive to the new drive formatted for Mac.
If you choose option 3 you can then format that older external to the Mac format and use both on the Mac without problems.
First of all thanks very much for the help. Could I do one of the following
1, Copy the photos from the external hard drive to the C drive on the computer the reformat the hard drive.
2. I have 2 4TB external hard drives so I could I think reformat the second hard drive to the MAC format, download from the first hard drive, move the photos then reformat the second hard drive.
Are both options OK?
Once again many thanks for your help
You can "Copy" the images (Not Move) to the hard drive on the Mac, which is called Macintosh HD as Mac OS X doesn't use Drive Letters like C, D, E and so on. Mac OS X uses Drive Names which can be anything you like.
So Yes you can COPY the images over to a Folder on the Macintosh HD then format the external drive using Disk Utility, found in the Utilities folder in Applications, to Mac OS Extended (Journaled) and give it a name of your choice. Also click the Options button and make sure the partition table is set to GUID.
Then you can MOVE those images back over to the external drive.
The only problem you will encounter is IF you copy over your LR catalog folder. It will be looking for images on the drive letter the external was assigned by Windows. You will have to point it to the newly Mac formatted external drive Name.
Fantastic. Thank you so much. Will pluck up the courgette do it tomorrow.
sorry meant courage. Bad typo
In reply to your message to me.
Did you copy over all the subfolder from the external to the Mac HD and then copy/move them again over to the external after it was formatted for the Mac?
Lightroom is not smart. I has no idea you changed system, operating systems and drive PATHS to where your images are stored. Old PATH LR is looking for.
DriveLetter of External Drive:\Folder Naming\Images File Naming.
New PATH where your images are.
DriveName(Whatever you called the external when you formatted it for the Mac)/Folder Naming/Image File Naming.
There is a feature in LR to Find Missing files. Once you use that all folder should show up along with the Drive Name you gave the external drive and the "Windows" Drive Letter will go away.
No need to Reimport and you shouldn't even try it as all those images are already in the LR Catalog file. You just have to Tell LR where all those images are now located.
Check out the Lightroom Queen website. I'm sure she has a FAQ or a tutorial on how to use the Find Missing Files feature.