The INSERT key on a Mac is '0' on the number pad

Yep. It is.

Useful for a number of things. If you're on a MAC, with Windows running in a Virtual, and you're running vSphere to log into an ESXi Windows VM, ... (take a breath) ... then you'll need to enter a CTRL + ALT + DELETE.

Which is actually, Ctrl + alt + Insert, which is in fact, Ctrl + alt + 0.

(That will make sense if you need to do it, it's just garbled nonsense if you're not trying to do it)

1. You are on a Mac.
2. You have VirtualBox
3. In VirtualBox you have a Windows virtual machine
4. You are running the Vshpere application in the Windows machine.
5. vSphere is connecting to a Windows VM on another computer (Windows #2).
6. You will need to issue the CTRL+ALT+DELETE command to that other Windows (Windows #2) to start it.
7. vSphere will accept CTRL+ALT+INSERT, however because we're on a Mac, we'll need to use CTRL+ALT+0