RAID ARRAY CAPACITY EXPANSION

Hello,
there is a server (Windows 2000) with two arrays.
Array A with 2 disks, Array B with 3 disks. Array A contain the system. Array B contain the data.
We want upgrade the Array B with new 145GB disk.
Currently we use 36GB disks. How to do this without lost the data ? Is it possible ?

Additional Info: Server W2K, Smart Array 5312 Controller, Adaptec 21960LP SCSI Card. 1 of 6 disk slots are free.

Thx…cooldba