a removable hard drive is a cheaper option than a flash or zip drive. There are two kinds of removable storage: internal and external hard drives.
The internal hard drive connects the same way that your main hard drive does, so using one of these requires an extra IDE connector in your computer.
External hard drives generally come with cases that make them USB adaptable to easily connect and disconnect them. In either case,
it is generally a simple process to put Windows XP on the storage device.
Connect the hard drive to your computer and start it as you normally would.
Insert the Windows XP installation disk,
and follow the instructions until you reach a part where it gives you the option to either perform a new installation or upgrade an existing installation.
Choose to perform a new installation.
Click on "Advanced Settings" in the next window.
This will allow you to select a location for the Windows XP installation. Select the removable hard drive you want to put Windows on.
Note that you may need to format the hard drive before installing Windows.
Follow the Windows XP setup instructions. The setup wizard will guide you through the rest of the process.