windows 10: I have deleted my C:WindowsSystem32driversect, what should i do?

The easiest way is to copy it from any working Windows 10 machine, most of the files in there are non-active and are mainly for networking information. Chances are them being missing will have no real effect on a normal system.

Lacking an existing machine you could download an ISO image from the Windows 10 download page and install it within a VirtualBox VM. You don't need to enter a product key because you are going to be using the VM for less than 30 minutes, far less than the 30 day evaluation. Simply copy the files from that machine.

The only active file in there is likely to be the hosts file, and even then it is only likely to be used if you have some special network setup or a system-wide adblocker tool.