Clean Installation Versus Dual-Boot Installation
There are three ways to install an operating system:
On an empty hard disk or a hard disk whose contents you don't want to keep— This is usually referred to as a clean install. The existing operating system (if any) will be replaced by the new operating system. You can also reinstall the same operating system over an existing installation to fix problems with the operating system (this refreshes the system files and settings) without losing user data. However, if you install a different operating system, in most cases your data as well as the old operating system will be wiped out.
As a replacement for the existing operating system (retaining existing settings and programs)— This is usually referred ...