changed to a bigger hd: how to use the additional space?

[Gerhard Reuteler]

Hi,
my pismo´s12GB ibm hd was very loud, so I changed to a 20 GB hd and all the 
partitions where copied onto the new hd. Of course the partition table is 
still the old one. How can I use the free space of the new hd? Is mac-fdisk 
the right tool?
Thanks for help
Gerhard