Resize OS Partition

Doing some work for a company who bought a server from Dell loaded with SBS 2003. Dell configured the system partition to 20gb and the data partition to 90gb. Problem is the system partition keeps getting low disk space warnings. Is there a way to resize the partitions to say 40 and 70? **Side note they also are using Raid 1 software replication through windows with dynamic disks. I’ve heard to many horror stories to trust partition magic.