If you do not intend to keep your copy of Windows installed on the computer, and you have made a backup of all of your important files, choose the Erase entire disk option from the Prepare disk space screen and then press Forward. The installer will automatically partition your hard disk in a suitable manner.

Partitioning does not occur until you finalize the installation, so you can decide to abort the installation at the very last minute if you require. After finalizing the installation, however, the hard disk will be re-partitioned and all existing data stored on it will be lost. Ensure that you have made and tested a backup copy of all important data.

For more complicated partitioning requirements, select Manually edit partition table from the Prepare disk space screen, and then press Forward. This will start a partitioning tool which you can use to partition your disk yourself. If you are unfamiliar with partitioning, please seek support through an Ubuntu support channel for advice on partitioning your hard disk safely and correctly.