Separate HD's kept separate?

I have 2 hard drives installed. One has Win 7 Ultimate and one has Win 8 Pro. I do not want each to see the other when it is booted up. One will be strictly work stuff and the other is to be all personal. So if I am booted up in Win 7 for work I do not want the other HD with Win 8 on it to be accessible and vice versa. How can this be accomplished?

Thanks in advance

I used to do that with BootIT NG, but I gave up on all such programs when I started Truecrypting whole drives. I'm happier with the reduced complexity. If I want to run a different OS, it's either a VM or a different computer. I'll never dual boot again, and I say that as someone who used to boot between as many as a half dozen different OSes.

I'm with craybob.

A VM or a separate machine is the way to go.

I use Virtual-Box myself, or Win 8 has a VM built-in.