I am a fairly new user in Light Room. I normally import photos by copying them from my pictures folder in Windows, to an external drive for storage and file management, which the computer designated it as drive E:. Recently I decided to try importing them directly from my memory card from my camera to the external via Light Room, and realized during the process that Windows had changed my drive designation for my external drive from E: to G:. I managed to correct the issue, but the last time I imported photos, I normally send copies of the RAW images to another folder in the drive, but I did not look, and LR tried to send the RAW copies to the folder in the E: drive. Since the photos were imported into LR, it will not let me access them again to copy the RAW images to the other folder. The question is this- can I copy the RAW files through Windows to put them in that folder in the external drive, or would I have to remove the subfolder in the catalog, and import the photos again through LR to properly complete the process?
You will find that some photos have question mark icons or exclamation point icons on them, this indicates that Lightroom does not know where the photos are located. These photos have to reconnected in Lightroom via this method: Adobe Lightroom - Find moved or missing files and folders
For future benefit, you might want to consider forcing Windows to not change your drive letter of this external HD, for example by assigning it a letter near the end of the alphabet (like S or T or U) and then reconnecting in Lightroom as described about.