FDISK cannot be used to change existing partitions.  It can only be used to
delete everything and start over.

Something like Partition Magic, such as BootitNG is needed to change the
existing partitioning without forcing you to start over.

Note that it is common for the partitioning to be slightly smaller than the
full size of the drive. Something other than FDISK might give a little more
control over this lost space, but not much.

Like Jeff said, you need some help as fdisk won't adjust partitions:

BootIt Next Generation is available from:  http://www.terabyteunlimited.com/
and it does partitioning, makes a compressed image, does many other
partitioning chores and is a boot manager.  It is not quite as easy to use
as Partition Magic but it is half the cost and has more features.  Unlike
the crippled PMagic demo, BING is a *full function* demo you can try for
FREE for 30 days.  The web site has a lot of support articles.