Re: compromised
If you have physical access and enough time then yes anything manmade can be manunmade however this does not mean that you cannot design something to be truely secure if you can discount physical access.
Without physical access computers should be secure in every sense but because, I would say, Microsoft's policy of putting security last lots of people, who do not understand low level coding, believe it is not possible to have a secure and bug free computer.
It is possible just not on a PC and especially not when users have root access