It will not be a problem at all to do what you ask.
Since the drives will be seperate drives, you can simply install Windows on one; for example if it's C: (The other maybe being D), and it will not affect the other drive, leaving the other open to anything else you want it for.
Once Windows is up, and the other drive you want to place data on isn't formatted yet; if its for example new, you can easily right click the drive, and select to Format it in NTFS.
This will then make it accessible for any media you wish to place upon it.
It gets slightly more complicated if you wanted to use one drive, and split them into two partitions or parts, but the Windows setup makes this pretty easy too.
It'd simply give you different partition sizes to choose from to split the data/programs the way you want to and perform the install as normal.
To Windows, the one drive would then be seen as two theoretical drives. This still provides you with a split (or multiple splits), but without needing two drives.
Sorry if you already know that.
To answer the RAID question, there are many types. The most common types are RAID 0, and RAID 1.
This is a list of the other RAIDs, and what they do:
RAID 0 is a striped array, in which you need 2 drives for it to function, and works in such a way that access times are a lot faster, so programs/games load quicker.
On the offset however, it means that if one drive was ever to fail, you'd lose all the data, since both drives are needed to mantain the entire image.
RAID 1 however also needs 2 hard drives, but one is simply a mirror, or a copy of the other. Within Windows, the 2 drives will be seen as one, and anything that is copied onto one, will be copied to the other.
The offset of using this technique is that you basically lose the entire contents of one drive, due to it being used as backup, BUT gain the knowledge that if one drive failed, everything would be safe. All that you would need to do, is insert a drive of the same model/capacity preferably (for performance) and it'd rebuild the array.
Its the way mine run, and have had one hard drive fail, but the RAID 1 array saved all my data from destruction.
You should always backup anyway, but it gives you that little bit of extra confidence.
I hope this helps