I agree that 30GB seems a tad small. When I redid my drive, I made the XP partition 30GB and the Vista partition 40GB.
You can use Gparted to do it. There's a bootable CD that contains gparted over at http://gparted-livecd.tuxfamily.org/
It is also on the CD they offer at: http://www.sysresccd.org/Main_Page
You'll have to delete the empty data partition and stretch the Vista partition to the size you want, then make a new data partition.
Note that if you use the "Novo" restore function, I have no idea what will happen to the partition size.
-Warr