I normally work with LR on my desktop PC where all my images and my LR catalogs are on a second HD in the box.  Work fine no issues.

Just recently purchased a laptop and would like to be able to work with images in the catalog on this new machine.  So I copied all my images and catalog to a 500GB external drive.  When I try to access the catalog with LR4 I get the message below.

I can write to the external drive so I don't know what the problem is.

Thanks
Ken

I don't use LR but Tim Grey addressed this in his DDQ. If I remember right, the volume name needs to be identical so the external would have to have the same name as the HD on the Desktop and the same drive letter. My memory isn't 100% clear but that's what I remember. I a certain you could easily Google this question or find an answer in Adobe's forums that is exact.

I found it, while not exactly your question, it is similar. Hopefully this will help:
http://campaign.r20.constantcontact.com/render?llr=gze8ludab&v=001CYMvdQv4AOjoiXQ-Rc7QdSMMI_ckhmoIW2zjUaS53LJoX7cDFfH5uF3MuAakgkpguIeKCIaOss-AUyi1rts9bPKDgx_VsbxIke5fN-rQB7Q%3D

I am on the rod a lot and do the exact same thing (I am actually doing it right now).

I have all my images, catalogs and supporting files on a hard drive named "Photo" on my desktop. Before I go on the road I just clone that drive's content onto a portable drive named "Photo OTR". It is OK for the drives to have different names. It is very helpful, though, to have all photo files in one folder, with the catalog and other files in separate folder. I simply named them "All Photos" and "Catalog".

When I open Lightroom from my laptop I will initially get little "?s" in the frame of all pictures in the Library Module. Then I have to go to the "All Photos" folder in the left side panel. This folder will have a "?" too; it indicates that Lightroom cannot find that folder. Control-Click (Right-Click on Windows) on this folder will bring up a box with the register. Navigate to the folder "All Photos" on "Photo OTR" and click on it. That's all. Lightroom now knows where to find you images because you have trained it to look for them in the right place.

When I get home I will have to clone "Photo OTR" onto "Photo" to have all updates and new images on my desktop. Then when I open Lightroom on the desktop I will have to Control-Click on the folder "All Photos" and navigate to "All Photos" on "Photo". This is because I have cloned the catalog that I used on the laptop onto the desktop and it is trained to look for "All Photos" on "Photo OTR". So it needs to be re-trained.

This all may sound more complicated than it actually is. It quickly becomes second nature.

One more thing: The reason for using different names for the hard drives is simply to keep track of what you are cloning onto which drive. When you're getting ready to go on the road you will clone from "Photo" to "Photo OTR (=On The Road)". Upon return you will clone from "Photo OTR" to "Photo".

Thanks for all the info.

What worked was to go into properties for the EHD while connected to the laptop and change permissions to allow the users on the laptop "full access" to the EHD.

Seems to be working fine now.

Jens, your description of this is how I will do things going forward.

Thanks
Ken