you can hide partitions with acronis disk director suite or norton partition magic of course naturally it will still show up in the bios post screen,im not sure youll be able to boot to such a partition without a special prog and even if youll find someway to get it done youll probably need special software to see the hidden partition content but again you can unhide the other partitions when needed
what about encryption?
truecrypt: http://www.truecrypt.org (virtual drive & entire partition or hdd)
bestcrypt: http://www.jetico.com (virtual drive)
drivecrypt: http://www.securstar.com (virtual drive)
drivecrypt plus: http://www.securstar.com (entire partition or hdd)
all the non-free ones have a more secure file hashing (sha1/ripemd have been cracked long time ago) these uses sha256,second of drivecrypt/plus unlike bestcrypt supports smart cards/fingerprint readers for better security
virtual drive means that all encrypted data will be saved to one encrypted file that can be mounted as a virtual drive (with password prompt and/or other hardware means of course) and can be used basicly like a normal hdd partition,much more comfortable then standard file encryption,of course you decide on the size of the enrypted file it can go as high as you want even gb's