I think having linux and windows on sepperate drives is the best solution for dual booting, though I ussually have linux on the first drive and windows on the second drive. That way if I have to reinstall windows, I can unplug the first drive from my mother board, reininstall windows, then plug the drive back in. NO problems with windows replacing grub as the boot.
As for partitioning your second hard drive for mint... I would suggest booting the live cd and then partitioning with gparted. Make 4 partitions:
Mount point | file system | size
/boot | ext2 | 100mb
/ | ext3 | 20 - 30 GB (this is your root/main install)
/home | ext3 | the rest of the drive space this is were you can keep all your files like music, documents, etc.
/swap | swap | same size as the amount of ram you have
Make sure to have boot at the start of the drive and swap at the end. The beginging/end of the drive runs faster.
If you want to have more than 4 partitions you will have to make a logical partition. You can have as many partitions as you like in a logical partition, but only 4 primary partitions are allowed on a drive. (as of right now) You don't have to have /boot on its own partition...but it makes things easier in the long run. Exspecially with reinstalls of linux or windows. (you'll end up doing this every 6 months with mint if you want the latest versions) Having your home drive sepperate is a must so you files will be safe after a mint reinstall.
After you use gparted on the live cd to set up your drive like this, write down all the drive information. like hdb1 = boot etc.
Then when you install mint and get to the partioner section of the install, hit manual. Then tell mint what partitions to use and how to mount them. This is all in drop down menus. Make sure none of your windows partitions are going to be used.
The only limiting factor of the Linux operating system, is its user. -Linus Torvalds