In Progress I think my laptop has been hacked

[PCGuy2]

I was checking emails, and I didnt clicked any link,neither I installed any add-on, I suddenly got alert to restart the pc to disable user accounts and it get restart automatically.
When it starts,after login screen its displaying this.

I have re-installed windows, and after reinstalling,I was just updating windows and while they were getting updated, it re-started automatically and after restarting the same screen starts appearing. I am very much tensed, what should I do to make it work again?
I have contacted the seller too,but they said too it seems that it has been hacked.

PS: I am using this laptop for last 9 months,and I purchased it brand new

[PeaceLily]

This looks less like a hack and more like a stolen computer, I'm afraid.

You mentioned contacting the seller -- was it purchased off Ebay? I suspect it wasn't actually brand new. Booz Allen Hamilton is a legitimate consulting firm, and this notice displaying on the screen looks like a standard corporation IT Acceptable Use policy. Maybe the PC has some kind of anti-theft software installed that suddenly triggered and locked up the system.

If I was you I would report the seller and try to get your money back.