NTFS security problem

im a little confused. i can set a strong password on the admin account,
encrypt data at the file or folder level, and assume im secure. but there
are many utilities out there (boot disks etc.) that allow resetting the
admin password from a command line. once thats done, all security is gone.
heres my question: i would like to know how to encrypt the contents of a
harddrive and ensure that not even the FBI can access the data, even if they
physically had the drive. is this possible? thank you