I didn't even show the drive letter (C\D\E\F\G) on my computer.

You open "My Computer-Organization-Folders and Search Options-View" and put a check in front of "Show Drive Letter".

If not, there may be a problem with the partition table. Your partition table is corrupted, and windows can't find the drive letter, so it can't see the data.

Use disk genius to find the previous partition, and then rebuild the partition table.