Comment 1 for bug 48338

Thanks for your report. At present, you must reformat system partitions (e.g. /, /boot, /usr, or /var) during installation; bug 47046 is filed to note that the partitioner should warn you about this up-front. If you are upgrading an existing installation, then please see http://wiki.ubuntu.com/DapperUpgrades rather than using this installer.