Securing data on disk - when disk taken out of computer ?

Hi, I'm seeking for solution, that would let me ecrypt partition of file on disk, but be somehow automatically mounted on reboot (without prompting for password) , but still secured if someone takes disk out and tries to mount on another system... I'm newbie, so please be gentle - it could be impossible to achieve... How to do this? Can I somehow sign disk to be used/mounted only in certain HW and not on another HW ? If proof solution is not possible, could I at least automate mounting of encrypted file and give at least some problems to enyone that stoles disk and tries to mount it outside PC ? Thanks in advance, regards, Rob.