Yes, deleting the windows partition and reformatting the disk will remove windows. You will need to change SuSE's default partitioning scheme. You should be able to resize your Windows partition to allow enough space to install SuSE.
One option is to use a separate hard disk for Linux: http://opensuse.us/viewtopic.php?t=580
Or alternatively run an openSuSE virtual machine under Windows using VMWares free player.