How do I open JPG files?

Photoshop cannot open cr2 and jpg files in a single folder on an external harddrive

• I can no longer open a number of raw and jpg files in a single folder on an external harddrive. What's going on? Is my harddrive about to die? Between some time last night and sometime this morning, a folder of pictures on my external harddrive has become almost entirely unusable. I'm using photoshop cs2 on windows xp. The pictures are all .cr2 raw files from a canon 5d digital camera. My workflow involves tagging and color coding the pictures I want to tone and edit, and once I'm done with the editing, saving a new jpg with the same filename as the original with an additional identifier that it's an edited version. I spent a little while working on the folder (toning in photoshop and captioning in photo mechanic) and then left the harddrive alone and turned off for the night. When I opened the folder in photomechanic today, a majority but not all of the files (both the cr2's and the jpg's) would not display. When I open the files in photoshop cs2, I get errors. For the cr2 files, photoshop says "could not complete your request because it is not the right kind of document." For the jpg's: "could not complete your request because an unknown or invalid JPEG marker type is found." Some jpeg's and cr2's in the folder work, and as near as I can tell, all other jpeg's and cr2's on the drive open without a hitch, as well. As such, I don't think this is not a problem related to my raw plugin. In some cases, the cr2 opens, but the edited version, a jpg, does not open. There's a possibility that, last night, while working on the offending files, the drive quit responding (could not do the "safely remove hardware" thing) and had to be restarted. Though I have backups of these files on dvd's, I'm still concerned. Is this a larger problem with my harddrive? Is it only a problem with these particular files that won't crop up elsewhere on the drive or my computer? Is there a way to fix the offending files?

• Answer:

  One more thing: the folder also has xmp files with my raw conversion settings for individual files. They have the same names as the cr2 files. All of the xmp files work just fine. Leads me to suspect photomechanic might be to blame.