Hi there,
I've been using RAID for years and is a cheap way of getting decent performance. If you haven't used RAID before each motherboard has a slightly different set up and your best friend in this instance is your motherboard manual. If you don't have it then try the motherboard website for a download..
Usually though setting up RAID will go something like this (I'll use my boards set up process as a guide as most boards will have a similar set up)
To first set up RAID you obviously need at least two drives preferably of the same size. You'll need to create what is called a RAID array which is just a term to denote drives which have been set up for RAID. To create the array you will need to press a set of keys whilst booting (sometimes you'll see a prompt like 'Press ctrl+F to enter RAID bios utility') it can be easy to miss and can take a few tries before you get into the utility.
Once in the set up utility you'll see a menu which will have links for creating, deleting and viewing drive assignments. Your obvious choice will be to create an array and from there you'll see a numbered list appear. At this point nothing will be in the list as you have yet to create an array. If you highlight the number one spot and then press enter a new menu will appear. It's from here you will be able to configure which type of RAID you desire, either striped or mirrored. There are different types of Striped or mirrored RAID and they are denoted by using numbers. Your usual RAID set up, when two drives are combined to create one, is known as RAID 0, RAID 1 is mirroring, when two sets of the same data is written to both drives and a full list of what they are and do can be found here:
RAID - Wikipedia, the free encyclopedia
As I said above your motherboard manual can be invaluable at this point or sometimes you'll get a separate booklet.
Once you've created your array and all is good you'll be asked to reboot, you'll need to change the boot order to boot from CD/DVD as is normal when doing a custom install. Windows installation is as usual although when you get to the screen to determine which drive you would like to install windows on, you may get the message that windows cannot find any drives. This is because the os needs RAID drivers to be able to see your drives. This is not always the case for every set up and as i said before this can differ from board to board. I keep my drivers on a usb stick but it is possible to pull them off a cd/DVD too.
Lastly when using RAID 0 it's an extremely good idea to keep a back up. If one drive goes down for whatever reason (a loose connection can do it and as happened to me although rare) then all data can be lost. I tend to just keep my third party apps,certain files/folders, emails and game saves backed up as reinstalling the os takes all of 20mins (even less under win 8).
I hope I haven't confused the issue for you and if you have any questions then please do ask.