How to compress data for backup SBS Server 2003 R1?

I have a client with a SBS 2003 server R1 who needs to back up his documents. He has over 200 GB of data and a SCSI tape drive. The default BU program will not allow me to either compress the data or deselect the OS and program files to free up space. Is there a work around? or a suggestion of a low cost/free program to accomplish this until we can deploy another back up solution