Find and read the instructions for your RAID system. With RAID1 systems I have used, you can do a process called "breaking" the RAID1 array. This effectively converts the array into two completely separate hard drives, one or both of which have ALL of the original data from the RAID array on it / them. BUT don't bet on that. READ your manual and be SURE what it says it can do, then follow the instructions completely.
Normally, if you try to remove drives from an array or remove the array, then all data will be lost. If you disable the raid controller and set your controllers to AHCI or IDE you might be able to make single drives out of the two, but like paperdoc said, it will vary from one motherboard to the next so read your manual. If you still can't figure it out, then it's always best to make a backup before changing settings.