I chose GNOME Boxes as it uses kvm. It was really fast and easy to install, I just needed my Windows-Installer-CD as an *.iso file.
However, I could not find any option to insert another *.iso image file to be mounted in the guest system. The user interface just does not provide to change the CD disc image - so we have to change the kvm options in another way. Open your terminal and type:
$ virsh edit Windows\ XP\ Pro.iso
(If you installed something else than Windows XP you might have to look in the folder .local/share/gnome-boxes/images/ how your machine is called.)
In this file search for the lines saying something like the following and exchange your iso-filename (+path):
<disk type='file' device='cdrom'>
<driver name='qemu' type='raw'/>
<source file='/home/tux/AoE.iso' startupPolicy='optional'/>
(If you need help using vim, check this out.)
Save it, reboot your Windows and enjoy having your disc image in the CD drive of the guest!