Three hdds config??

The only thing RAID can do for you is to combine two or all of these into one "drive" through a version called "JBOD" for "Just a Bunch of Drives". RAID0 or RAID1 will limit your 2-disk array to the smaller of the two drives in the array. You could not possibly use these three together to make a RAID5 array of any useful size. And RAID 0+1 , etc, has similar limits. Consider also that using RAID in any form means you MUST have the RAID system working in order to use those drives.

The question arises, why? Using each as separate drives makes more sense to me. You can organize your data any way you like, and having it spread over 2 or 3 drives means trouble on one drive will leave your others safe.

Some people like to have a smaller Partition to contain only the OS, and put all application software and data on other drives. They argue that, if the OS gets corrupted, they can completely re-install it on that small "drive" (Partition) and still have all their other stuff preserved safely. You have that situation already, although I am not sure whether 40 GB is enough to install and run an OS. I think so. And the Partition truly is a completely separate physical drive. Look at this option, and make sure you understand how to install all your application software, My Documents folder, etc. NOT on the C: drive you boot from.

If you're installing a new copy of Vista or Windows 7 from scratch then use AHCI mode. IDE mode is really just for backward compatibility for older OSes like XP which don't include SATA drivers.