Norton/Symantec Ghost or Drive Image Pro.
Either one should do the job nicely. Ghost from the 30 gig to the 15 gig, format the 30 gig, transfer the ghost image onto the 30, & then restore from the 30 to the 15. Or you could create a second partition on the 30 gig & avoid using the 15 until you're resdy to restore the image.
Viper GTS