If you want a completely new Xandros install, and the SUSE install in small enough, you can just do (from a livecd would be best):
Code:
rm -r /mnt/d0xandros/*
cp -Ra /mnt/d1suse/* /mnt/d0xandros/
which will wipe the xandros partition and then put the SUSE files in its space. Then you can do a new xandros install onto D1.
If you want to preserve the xandros data, you'll probably need a backup drive or something.