I’ve found a very nice solution to a problem that has plagued me for a while and perhaps has troubled you also. (It is a Windows problem so Mac users may now go to sleep or go get some chocolate!)
I have several external hard drives, some of which I keep offline and turned off to avoid trouble with heat or power surges, etc. They all contain images which are referenced in Lightroom catalogs. The problem is whenever I plug in another a thumb drive for a quick file transfer, a card reader or other USB device, the drive letter assignment for the external drive(s) get scrambled and Lightroom reports that filename xxx is offline or cannot be found. While it isn’t impossible to either help Lightroom find the files or to go into Start/Programs/Administrative Tools/Computer Management and reassign the drive letters, who wants to do that on a regular basis?
Well a little web research turned up a neat tool for taking care of this nuisance. It is called USBDLM and written by a fellow named Ubi Sieber. It runs as a Windows Service, is easy to install, its versatile and is freeware. I’ll leave you to go to his website and get the details. There are far to many configuration options to go into here but one thing I found that impressed me highly was that you may set a permanent mounting for a specific drive by identifying it’s DeviceID in a .ini file. For me, that’s about as fool proof as you can get. You can also tell card readers not to use a drive letter unless it has media inserted. (Multi Slot Card Readers can eat a lot of drive letters even if the slots are unoccupied and make life difficult.)
I’ve installed the service and am ecstatic about its performance. (As always, the caveat…”Your mileage may vary.”) If you’re having dancing drive letter problems you may want to give this utility a try.