RAIDing only part of a hdd?

so I have 2x80gb hdds. And I want to isntall win and linux both…

Is there a way to RAID the hdds together so it contains 2 different filesystems?
or…
basically… what I need to do is for example to RAID the 1st hdd and a part of the 2nd together and then spare the other part of the 2nd hdd for the linux

I have a feeling it’s impossible :puzzled: