UNetbootin allows for the installation of various Linux/BSD distributions to a partition or USB drive, so it's no different from a standard install, only it doesn't need a CD. It can create a dual-boot install, or replace the existing OS entirely.
* Microsoft Windows 2000-Vista, or Linux, or a USB Drive.
* A broadband internet connection to download the distribution packages (unless installing from pre-downloaded media, see below)
* Spare hard drive space to install the OS in (varies depending on distribution)
These details are provided for information only. No information here is legal advice and should not be used as such.