Looks like the "Compress" attribute got set on one of my EDB files. Not sure how it happened, but it did. So, of course, Exchange won't mount it now. The DB looks to be in a clean shutdown state, so I'd really like to just uncompress it and move on. However, every attempt to do it from Windows GUI or the command prompt seems to just hang. The DB is about 300GB, not sure if that's why. In any event, I was thinking that I could copy the EDB file using robocopy to another location WITHOUT copying any attributes. Then delete the original, copy the uncompressed version back and attempt to mount it. Does that sound like it will work? At this point, I don't really care about saving the logs.