>Anyone know how I can take a look inside to see what the mybackup.sql file contains?
It's only a plain text file. You can use any text viewer to open it, or
shell> more /path_to/mybackup.sql
If you don't use a user and password, it will only contain the error message that you couldn't connect, unless anonymous access is allowed, and you'll get the test database.
> I kept getting a "Got Error:1045 Access denied for user "root@'localhost'".
Can you open the mysql command line client with mysql -uroot -p ?
If so, then should be able to invoke mysqldump with the same user/password.
If not then you'll either need to find root's password, or reset root's password.
Good luck,
Barry.