How to re-partation a mirrored SBS drive

I have a Dell Server PESC420 running 2003 SBS with 2 80GB drives that are mirrored. Drive C: is 12 GB and drive E: is 67 GB.
I would like to make the C: drive 25GB. Is there any software that will allow me to do this, without deleting the volume and starting over, and having to re-install everything.

TIA to anyone who can answer me.

Robert Payne