[QUOTENB - given physical access to a Windows PC or server (not domain controller) even I can hack the system and change the admin password][/QUOTE]
it used to take us 5 mins from getting a machine through the door to raping it of all passwords of every network it had ever been logged into. We had the password for the US mil network for 6 days until someone phoned them up and told them that we had it. Domain controllers used to take 10 mins once we had physical access and I used it many times to save a network from an admin that went rabid just before they left.
And to note it was the desktop general admin password we got for the US mil, not the secure networks. Thankfully they use unix for proper security and blokes with guns stopping you getting near the servers. Once you have physical access to a server you are knackard.