2) you don't have to install intel matrix storage manager if you want to do RAID.
The raid setup can be done by CTRL-I. The raid driver is installed during xp/vista setup. The intel matrix storage manager gives you a GUI so you can manage your array and settings.

If you have a bootable windows or can boot to windows already, you can attach more drives in remaining SATA ports. Go to bios, go to sata and change mode to RAID. When the system reboot, you can CTRL-I to create raid set OR just boot to windows, install MSM, run it and create the array using the GUI interface.