It's very easy. It's basically the same as dual booting a single drive w/o the mixing of win/lin partitions. Usually it's better to have win on your 1st hd (drive 0). Your second hd you can format as one large primary partition, or as 1 large extended, to keep things simple.
Probably the most difficult decision will be deciding how to boot your system (e.g., floppy, lilo, grub or other; floppy being the simplest).
Check out the HOWTOs at the Linux Doc Project (http://www.tldp.org/HOWTO/HOWTO-INDEX/categories.html
) & also the docs at Mandrake User (http://www.mandrakeuser.org/docs/index.html
). They provide a great intro to Linux.
Just be sure you're installing onto the right drive (you know how Linux labels drives right?).