I have a laptop that currently has XP pro on it, however I am wanting to also install either Vista Business or Windows 7 Beta.

I can make a new partition fine, but what I am wanting to do is encrypt the Vista/7 Partition while leaving the XP partition unencrypted.

The PC would boot to XP by default, or Vista/7 if chosen at boot loader, and there should be some sort of authentication before Vista/7 would boot.

Has anyone done any installation like this and can offer any advise?

I looked at TrueCrypt but that doesnt seem to be able to encrypt the secondary partition without using massive amounts of disk space, and possibly a reinstall of XP, which would be a real pain.

I have also looked at BitLocker but unsure if this will work either.

I would ideally like to be able to access the encrypted partition through XP with authentication however this isn't a requirement.

Any advice?