RAID1 plus non-RAID partitions?

NO! RAIDs have to be the whole drive(s). The only way you have "leftovers" is with drives of different sizes.

Since you have 2 very large HDD, you can partiton up one, and use it for different OS/Programs/Games (i.e. Windows 7 on partition 1, Windows XP on partition 2, etc., each with all the programs you want on each OS). Google "Dual Boot WIndows 7 and Windows XP" for more information, and detailed instructions on the how-to's.

Then, for the second drive, use it as a back up for the first drive. RAID 1 is not a viable backup, it only saves you in case of drive failure, which won't work with what you wanted to do. And it doesn't save you from errors, viruses, or malware.

Or, use the first drive for the OS's, and the second for your "Libraries" (i.e. My Documents, Downloads, Music, Pictures, Videos, and Gaming Data). This will keep this data safe and separate from the OS's, and you can "point" the OS's to this data when needed.

Or, use the first for OS's, and the second drive partition up into 2 parts: one for your Libraries, and one for your back ups.

Nevermind! I just re-read your OP, and this is what you should do:

1-SSD: OS Drive (you can partition is up for multiple OS's depending on size)

2-HDD: Librairies (My Documents, Downloads, Music, Pictures, Videos, Gaming Data)

3-HDD: Back Up for both. You can use Windows or Norton back up. But I like to use Microsoft SyncToy 2.1. I can set it up to back up what I want, where I want it. But, you have to run it manually. Then I edit both Windows and Norton's back up utilitizes, so I don't create mutliple copies of the same stuff.

See my signature below.

So, what brand, type, and size of your SSD?