RAID 1 Question

[FiberoN]

I am planning on buying another Seagate 120gb sata drive for a RAID 1 as I have already had a drive fail me and I don't want that to happen again. If I buy the drive now, do I need to reinstall Windows on the new array or can I just install the second drive and use the RAID software to copy all the data from the drive I have now into the new one? I don't want to lose all my data or have to backup all my stuff to cd's.