Ghost v14, Vista, and System Restore

I'm using Ghost v14 to back up to an external hard drive on a Vista computer.  My external hard drive is reaching capacity too quickly due to Vista system restore points.  By default Vista creates a system restore point each day and, also by default, Vista systems allocate up to 15% of the total internal drive capacity for system restore points.  This lack of flexibility in the recovery point utilization presents a problem when the interal drive is large.  Is there a way to limit ghost backups to only the most recent recovery point either through an explicit command or a script?  Alternatively, anyone know how to modify the default recovery point behavior in Vista?

 

Thanks.