Delete, Merge, Create, And Rename A Hard Drive Partition Without Formatting Windows

When you format your computer you are asked if you want to create partitions on your hard drive. I definitely recommend having your hard drive at least halved and made into two partitions for starters. This is not unreasonable as most hard drives in computers now days are getting rather large. Therefore you can afford to spare some extra space to store files away in case of a computer crash.
To actually change, rename, merge and delete partitions on your hard drive while not effecting your C: drive you must have partitioned your hard drive in the first instance.
If your hard drive is just one big partition called C: drive then you cannot just chop a bit off later when you feel like it. See How to delete a partition on a hard drive when formatting Windows.
However if your 100GB hard drive is already divided into two partitions of 50GB each, one being the main C: drive and the other is left for you to play with.
Why is it good to have a hard drive divided into partitions?

There are benefits to having your hard drive divided into separate partitions and the main one would be to backup important files. If you have files stored on another partition and C: drive crashes, it is most likely that your files on the other partition will be fine.
Another benefit is that you can format C: drive and leave the other partition intact and still storing your important files. You still go through the normal steps of installing Windows XP but you just choose to delete the C: drive partition only and then recreate it and install Windows on it. This leaves the other partition untouched.
Having partitions on your hard drive also allows you to organize your computer files better. Some people have a separate partition for different types of files.
How to create a partition on your hard drive without formatting Windows:
If you have a partition on your computer beside the C: drive, then you can delete, merge, rename and create more partitions.
Go to the start menu and select my computer (just make it blue)
Then right click on it and choose manage from the menu
Open the storage section by pressing on the plus sign in the left column
Then choose disk management
All of your partitions will show up here