Setting up existing system with multiple OSs to multi boot

Hi, I think I should be able to use grub for this but I m not sure how.

I have three discrete HDDs all with entire drive given over to single OS (plus whatever extra swaps, helpers, efi boot loaders etc)

I have Ubuntu 12.04 (primary OS)
Hackintosh 10.7 Lion
Windows 7 Home Premium

All these drives are in the same case and connected individually would all quite happily start the same system as they were all built in it at various points.

I don't really want to blow any of them away (Lion is the cleanest and so least painful if I have to).

I had hoped I could do this from the 12.04 install disc/something else but it looks like it wants to do an over-the-top reinstall and I'm not clear what that's gonna do to my data...