Installing VirtualBox has broken my remote desktop - how can I resolve this?

Do any of your VMs have remote display enabled? This binds by default to the standard Windows remote desktop port (3389). If a VM is using this port, Windows won't be able to use it for remote desktop. See the manual for more discussion on how to change the port.

"I also installed VirtualBox remotely and it broke my Remote Desktop connection.

My experience is this: The Windows firewall seems to have been resetted.

One solution I can give you is this: Connect your keyboard, mouse, and your display to a remote machine and re-setup the firewall again. In my case, my HDTV does not have a VGA input and I don't have a VGA monitor, so I have to put in my video card with DVI-to-HDMI adapter to control my server directly.

It's a pain, but it seems to be the only way UNLESS there's a way to remotely configure the firewall (but a firewall is a firewall and I doubt this will happen).

PS: While in the subject of firewall and in a different subject from Remote Desktop and VirtualBox, from my computer in an internal network, I tried to access my website in my server and port 80 has been blocked. This is after I install VirtualBox with networking support."