No no, you do not need more than one partition on a drive in order to store files. You can use the entire 80GB. Multiple partitions are optional for organisational purposes of your own preference. I hope I haven't confused you
A partition is just a defined area on a hard drive
. So when you format the 80GB drive, there will be one
partition, being the entire 80GB of the drive.
Multiple partitions are when you split the drive into more than one
partition. For example, splitting the 80GB drive into two 40GB sections results in there being two partitions, each with heir own drive letter.
So technically speaking, when you buy a new hard drive from the store and format it, you're already creating one partition.