Have you posted the question on the Lightroom forums? They are very helpful and solved some of my problems. I would do a search first because this might be a fairly common question.
Lightroom Forums
---------- Post added 02-07-15 at 01:35 PM ----------
I might add that when I did this a while back I simply restored from a backup. I routinely backup to two usb drives. One drive is for the entire system, the other only for all my generated data. I also keep the a second copy of the Lightroom catalog backed up to a folder in my Photos folder, so that it gets backed up to the usb drives each time I perform my weekly backups. When I lost the drive in my laptop I simply restored everything from the backup drives. If a different laptop all together I would do a general OS installation then my programs (like photoshop, lightroom, ect). Lastly I would restore from the backup from the usb drive that contains all my generated data, which would include photos and last Lightroom catalog. Then when you open Lightroom just direct it to the catalog contained in the restored folders. At least this worked for me.