@Kvist:
Always keep your original disks write protected !!!
If it asks you to write enable a disk, there is something wrong. You should never write enable your original disks. If you need to write to a disk, make a backup first.
And as already mentioned, never ever run Installer in novice mode. Novice mode makes assumptions which are nearly always wrong. This does not only apply to the Workbench installation but to all installation scripts which use Installer.
Bye,
Thomas