to select ONE of the files and delete the .dcm portion and see if it now opens (sometimes malware will add extensions). If it does not open add the .dcm file extension back onto the file name.
If the files are on Western Digital MyBook drive the DCM extension was added by Western Digital Mybook software, at least according to this website - http://filext.com/file-extension/dcm
If the first thing works just get busy re-naming files. If it didn't work here is one converter (not free) -
some files i scanned in awhile back as jpg now have a dcm extension after jpg. as in, mypicture.jpg.dcm. and now i can't open them!
i don't even know what .dcm stands for (LOL)
(i have no idea why the extensions are there but i need to access the info. my laptop crashed & i reloaded lots of the info from a backup/recovery drive.)
using xp on an hp laptop, scanned on epson flatbed.