1) Checking if you can extend the current disk or need to add a new one
This is rather important step, because a disk that has been partitioned in 4 primary partitions already can not be extended any more. To check this, log into your server and run fdisk -l at the command line.
To disable the firewall in the currently running profile, you can issue the command:
netsh advfirewall set currentprofile state off
And re-enable with:
netsh advfirewall set currentprofile state on
Note: If your Hyper-V is internet facing, disabling the firewall is not recommended.