Backing up the web site files is simply as easy as copying all the files to another directory.
However, this may or may not address the backup of the web site database. If you're using SqlExpress then your database is probably in the ~/App_Data folder. Consequently, copying the files would also create a copy of the database.
However, if you're using SqlServer then the database will not be a file that you can copy. In the case of SqlServer, SQL Server Management Studio should be used backup the database prior to attempting the upgrade.
Thanks for reporting your experience.
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