You could first partitionate your disk using this tool: Partedmagic , then install openSUSE in the partition(s) you dedicate to Linux. It’s one of several ways to proceed, but it’s safe and simple enough. Just select and format the wishes Partitions during openSUSE setup. Don’t forget to reserve a Partiton for swap (=~ 2 GB ).
So you can open YaST / System / Partitioner and Select the Yes Button to enter the program. On the “Available Storage on YourPCName” window, you should see an entry for your new hard drive. It might say /dev/sdb for instance. Right click on the new drive and pick Add Partition. You must pick a size in Gigabytes, pick a type like ext4, you should format it and you must pick a folder name for it to be mounted, like /Software or /Data for instance.
You can not create a Windows NTFS partition using the Partitioner, so you must use Windows to do this. But, once you have created a Windows partition, you can use the YaST Partitioner to select a mounting folder for use in Linux. Start the Partitioner just as before then right click on the new Windows partition that might say /dev/sdb2 for instance and select edit. In the Partition Edit screen, the format command is not selected by default and leave it that way. You just need to add a folder name for it to be mounted in Linux like /Windows for instance or /windows/D. Keep in mind capitalization does matter in Linux and is used with folder names.
The drive names /dev/sdb are for example only as I do not know for sure what your letters will be. Let us know if you need any other help.
If you want to be able to boot Linux on the second HD, you’ll have to install Grub, the Linux bootmanager, in the MBR (first sector) of your first HD. This is not the default ! So look at the boot options and avanded boot options carefully (you will have to click some buttons) during setup.
It’s not going to hurt other operating systems on your first HD. However if you don’t want to touch that disk at all, it’s possible too, but you would have to switch HDs boot order each time before booting Linux.