Why have my tiff files on my external hard drive been converted to CR2 files?

Question

I've been using Lightroom 3 with an external hard drive for a few years now with no problems.
I shoot raw with my Canon t1i and jpg with my Canon SX-10.
Just last week I hooked up my external hard drive and Lightroom wouldn't connect to it. Usually when I hook it up, Lightroom opens up automatically. At least it use to.
I looked at the drive and it seems the tiff files are now called CR2 (Canon Raw I think). Any idea why this happened and is there a way to get them back to where Lightroom will recognize them?
I can open them in Photoshop, but not Lightroom. I usually go first to Lightroom, then to Photoshop and back. Can't do it know though.
Thanks for any help.

Answer 1

The TIF files may come from when you do a round-trip to PS and you either create a temporary TIF file on the way into LR, the default is to have –Edit.tif as the last part, or when you’re in PS and save any additional edits back to a TIF file.   This LR-PS-LR processing may have created many TIF files that have the same base name as the underlying CR2.  Both the CR2 and TIF files would have been visible in LR so maybe you’re remembering one extension more than the other.
The files you originally imported into LR would have been the CR2 files.   What has happened to their location in the time between  you originally imported them and now when you’re trying to hook things back up?   If they’ve always been on the external drive then maybe the only thing wrong is that the drive letter has changed, but if you moved the files from their original location on the local drive to their archive location on the external drive, then did the folder-path to the photos stay the same, at least most of the path? 
The way you normally fix things if the drive letter has changed or if the path has changed only a little, is you locate the file in LR’s folder structure, then right-click on the folder at the lift and choose Update Folder Location, then click over to the place on the external drive where that folder is, now, and click Ok.  LR will hook up all the moved photos in that folder.  The higher up in the hierarchy you locate the missing folder, the more folders underneath will automatically get updated.  If you give us some information about the specific locations of the folders in LR when on the local drive and on the external drive, then we can give more specific advice what to do.