Missing Files

DJ, thanks for your tips but I may not be fully communicating my problem. I know thumbnails are simply links to the real files in the real folders on the hard drive. I've moved my shares of files over the years but this time all I did was to move my computer and hard drive from one building to another and then rebooted. Why should that cause the files to not be found in the same folders they were always in? And why should all the question mark thumbnails in a LR folder be drained when I do a Find File and click on their real location. The LR folders are for the same remote drive in the same folders they have always been in. I tried the All Photographs thing you suggested and it found a photo in the file where it should be on my hard drive. I then did the "find in library" and it took me to my folder but it still has a Question mark and says it's not there - where it just told me to look. I know its in that folder on that hard drive. I tried importing photos back into their folders but they are all grayed out thinking they are there. An option would be to continue what I was doing earlier where it removes all the thumbnails and repopulates folders on the hard drive under a second listing for that drive. I'm just concerned that when I do that to thousands of photos and then delete the hard drive name that's empty - it's going to cause some problems. However, all indications are that it doesn't recognize the original hard drive anyway.  I don't mean to frustrate you and you don't need to respond unless you see something I'm obviously doing wrong. Thanks, Craig