I had problems with Backup and Migrate because it did not copy all of the drupal installation, themes, modules, views, etc and produced errors. I did it manually. I copied the database so it became an .sql file not a tar.gz or zip file. I copied all of the Drupal7 installation to the new hard drive space. Created the new database with the same name and password as the old version, did a mysqlrestore to insert all of the database information. It does not have to have the same database name, username and password but you will have to make alterations to the settings.php if it's not the same as the old version.
Checked settings.php to see that it pointed to the correct database and password. Went into mysql> show databases;>show tables; to see that everything was in place and comparable to the original.
Then started drupal 7 and it worked as though it was still on the old system. I ran update.php to make sure that the database was corrected. It works. And I did not have to fiddle with versions of modules and themes, etc.
That was my little adventure. Roger