Installing xubuntu on a new WIndows-8 system

[Joep L. Blom]

Hi,
I just bought a new system (Acer) which of course I couldn't buy without 
an OS so Windows8 is pre-installed. It uses several partitiona and First 
I thought of removing it completely. However, I've paid for it so first 
let it be (by the way it is completely unusable for somebody who has 
used UNIX/Linux over the past 25 years).
Now I have shrunk one Windows partition to 250 GB to install Ubuntu on.
However, when I start installing the first thing that's asked is a 
device for the boot loader installation. I give /dev/sda6 (which is the 
partition I would use for Ubuntu) but it complains that it is used for 
mount point / (natural) and it want a separate partition for the 
bootloader code which should be marked as a "Reserved BIOS boot area".
I assume it will need an area for the grub loader in the boot-area but 
there is of course already the WIndows boot code.
As extra information: I install in legacy mode as UEFI is too new for me.
Joep