My name is Ankit and I work for the Social Media and Community Team at Dell.
As you are getting the message for boot mgr missing, so you can restore the computer to factory default setting.
To access the Dell factory image restore, you can follow the following link.
Kindly select the operating system for your computer & follow all the steps to restore the system to factory default settings.http://support.dell.com/support/topics/global.aspx/support/dsn/detectos?type=force&lx=181316&lv=336966&l7=362066
For any further queries, feel free to reply back on the post.