You don't even need two hard drives. Just divide one hard drive into partitions and install windows on one partitiona and unix/linux on the other partition. Use a bootloader to choose between the two at startup. Hope that helps, you can find lots of tutorials on the web about installing linux and windows.
If you install another hard drive windows will recognize it automatically. Just make sure to set the master/slave jumpers and tell the bios to recognize that hard drive.