iTunes seems to freeze when I ask it to locate missing files

I had been storing a lot of my music on an external hard drive, but I just moved everything over to a new folder on my C: drive. I expected that iTunes would not be able to locate my files at first, so I found a song in my playlist I knew I had just moved over, tried to play it, and then when the prompt came up that it was missing, I manually told iTunes where it was located. So far, so good.

Then, iTunes asked if I'd like to automatically locate other missing files, as I expected. I said yes. Since they are all in the same folder, I figured all the songs I'd moved over would be able to be mapped. However, iTunes has gone completely unresponsive and it's been over a half hour now. There is no progress bar, no popup window, nothing to indicate that it is actually in the process of finding these files. I moved over thousands of songs, so I figured it would take a while, but now I'm in a situation where I have no idea if iTunes is actually doing anything, but I don't want to force quit the application just in case it is and I mess something up. Worse, it's been playing music continuously (since I kickstarted the process by playing a track) and there's no way for me to get it to stop since no buttons in the interface are responsive, so I've had to totally turn my computer's sound off for now. The song titles at the top are changing as tracks finish and new ones begin, but the timestamp is stuck on 0:00 for each song.

Can anyone advise on what I can do here? Is it safe to force quit the application and do this at another time, perhaps when I go to sleep, so it doesn't cause this issue while I'm using the computer? Or is it possible that doing that might corrupt files or screw up my playlist? Is there any assurance that iTunes is actually working on finding these files, or is this likely to be stuck until I restart the application? Any way for me to see a status or *something* to indicate the progress, if it is working? Any help here would be greatly appreciated. Thank you!