You didn't mention what drives, or what motherboard, so I'll generalize.
So you've lost use of the PC? I assume so if one drive is "damaged." So you'l have to reinstall everthing: OS, programs, games. All is lost if you didn't backup!
First, you need to get a 1TB hard drive. I suggest Samsung SpinPoint F3 7200rpm 1TB. Seagate Barracuda 7200.12 is another choice. Try newegg.com
Second, during BIOS post, enter the RAID setup and remove the disks from the array. How to do this varies, on mine during RAID post I enter <Ctrl>+<I>.
Then enter your BIOS and set the SATA ports from RAID to ACHI.
Then install the new drive. Boot to make sure BIOS sees it correctly, it should. Set the boot order the HDD first, then optical drive second.
Then install the OS, via the CD/DVD.
Anything other than that, ask.