What would I want to partition my hard drive?
Answer: When you partition your hard drive, you create different sections of it that your computer reads as separate disks. One reason for partitioning your hard drive is so that you can install multiple operating systems on it. For example, Linux needs to be installed on its own partition in order to work. Another reason to partition your hard drive is so that it will read data more efficiently. If you have a large hard drive (20 GB or more), it would be wise to split it into at least two partitions. This way, the hard disk doesn't have to scan as much to find files. It also allows data to be stored in smaller block sizes, which means more space for your files.
To partition a hard drive that has already been formatted (and which you don't want to erase), you can use a program like Partition Magic, which will create a new partition on a hard drive without erasing any data. Otherwise, you can use your operating system's drive setup program to initialize and partition your hard drive. Though this is the best way to partition your drive, it can only be done by erasing all the data on it first.