if he tries to mount it with cd /Applications/TrueCrypt.app/Contents/MacOS ./TrueCrypt -m headerbak /dev/usb_device_name I don't think he needs to worry about anything. That mounts it with the embedded recovery header, but it doesn't replace the potentially corrupted header. I suppose it cannot hurt to back it up before trying ./TrueCrypt --restore-headers /path/to/the/usb/device as that replaces the potentially corrupted header with the embedded backup header, however I wouldn't be extremely worried about it simply because it would only cause a problem if the embedded backup header is corrupted but the original header isn't. Still good advice to make a back up though.