Bet it's a virus. That dos prompt is the virus disabling your internet I'm sure. When you reboot your pc does a dos prompt come up very quickly during
windows load?
I'd try booting into safemode, and running a virus scan, etc.
If there isn't anything important on the pc I'd just format the thing and not even waste any time. That is if it' a virus!
I had a virus that did something similar a few weeks ago and after 2 days of trying to remove it just formatted. Luckily it only infected .exe files so I just backed up my other stuff put it on my external and formatted.
nothing like a fresh install anyways!