Partitions

If you looking to change the partition structure, without having to re-install files, you need a partitioning utility such as Partition Magic.

If you have un-assigned space, you may be able to use fdisk.
You may need to define an extended dos partition, and/or define logical drives.

Without losing the stuff already on the drive, you will need to purchase one of the partition managers (Partition Magic, System Commander, etc) and follow their directions.

If you don't mind losing the stuff on the drive then you can boot to a boot disk (assuming Win95, 98 etc), and run fdisk and delete all current partitions and then recreate a primary and all the other partitions you want.

the only thing I would add to the other answers it which O S are you using ? if you are running X P then you must use partition magic version 7 for it to work and its dead easy.
G