i think it is saying you have not designated a partition to be the "/" root partition.
so you have windows and at the partition part of the install you chose manual.
Now leave the windows partition alone.
You can delete the partitions setup by suse and create a new / and swap partition.
you can select you old suse / partition (the reiser one i expect) and edit it, making sure its mount point is set to "/" root. (no quotes) the default file system used is ext3 but you could leave it as reiser, just make sure it has a format tick by it.
then carry on installing