I am a long time Dell PC user and purchased a new one on line a few weeks ago.  (Desktop Inspiron 3847 Windows 10)  Followed the "Quick start guide" to start PC; but did not get past the 2nd page.  Error message was something like: "you are locked out, consult administrator"   My optical mouse (new) could not work (no curser).  After "enter" new page with "password" appeared (I have not entered any new password).  After many attempts with on-off switch with no change, called Dell for support.

Dell support had me remove power cable for 10 seconds and a couple of times with on-off switch.  They said my computer was infected by some sort of virus (from my Verizon internet).  They then sold me a Microsoft Security software package for $389.99 for 3 years (which they upgraded to 4 years because I had ordered PC with the Microsoft Office 365 for $69.99 each year.  Finally, they will be sending me an empty box to return my new PC and they will send me another.

Questions:

1.  Was the brand new PC disabled by a virus?  If yes, was there no way to fix PC without having to send it back to Dell?

2.  Was the purchase of the Microsoft Security software necessary, because I found out later that it included 4 years of "Premium Tech Support:"  (from Stonefield IT Services LLC)