No problem. Forgive me, but I do not speak Danish, so I will try to be descriptive as you requested.
"Boot the machine" basically means "turn it on". In this case, John was instructing you to turn your computer back on. "Boot" is an English computer term which basically means "turn on" (comes from the term, "lifting from one's bootstraps", and no I have no idea who came up with that).
Even though what is said in the DOS window is in Danish, please give it to us anyways. Leave it to us to attempt translation as to what is said - the numbers and things which should come out and the order of which they come out will most likely be the same "shape" and "form" as the English command, and we can always use something like an on-line dictionary or
Babel Fish to translate into English.
I'm sorry for the inconvenience and the language barrier. We will try our best to make this as smooth and painless as possible. The Techsupportforum staff is multinational, many come from different countries, and if we have difficulty understanding, we'll try asking them to help clarify anything. If necessary, we may have to ask you to describe what is being said if we're having trouble.