RAID1, as tomatthe said, is only a secure way to keep file duplicates around in case one of the two drives dies. All it does is allow you access to the FILE when in reality it's on both DRIVES but you only see one physical drive in Windows. Handy, mainly for servers and high-end workstations where data integrity is key (power outages, longer-lasting systems, etc). For the normal end-user it won't really benefit you much.
In a nutshell, both copies of the file would get infected anyway, should you get some malware of some kind, so absolutely not: RAID1 is not helpful against malware.