I just did the command:

copy C:\Alpha C:\Test.bak

This created a .bak file on C:\. Now, what can I do with this? Is there any way to turn the .bak file back into a file folder? What are these .bak files used for?

You now have two files with identical content but different names. Whatever program created C:\Alpha must now be used to read c:\Test.bak.

.bak files are generally backups of other files created before amending the original file for recovery purposes should things go wrong.

You have posted in the Stand-Alone DOS forum, you should be posting this query in the Windows XP forum.. and post EXACTLY what you are trying to achieve

Good luck

If c:\alpha is a directory instead of a file then I think you've merged all the files in that directory into a single file. It's akin to the command copy file1+file2+file3. . . .

As far as I know there's no way to 'unmerge' them.

.BAK files are often just backup files. The only dos command I remember that automatically creates them is the old dos command edlin, an editing program. When you modified a file with edlin it would rename the old file with a .bak extension. Otherwise you would just manually rename or copy a file as filename.bak.

If you want to make a copy of a directory with the copy command the destination directory must already exist. So when you used COPY C:\ALPHA C:\TEST.BAK, if test.bak was a directory on C: then the files in alpha would be copied into test.bak. If test.bak doesn't exist the copy command assumes you want to merge the files in ALPHA into a single file named TEST.BAK.

Also the copy command won't copy hidden files or the contents of any nested sub-directories.