firstly have you used linux before? / installed an OS before?
Firstly make sure that you have backed up everything on your windows disk, but I bet you have already done that.
Secondly turn off the computer and restart it with the SUSE disc one (which version of SUSE do you have?) in the drive, you have to make sure that you have set the BIOS to boot from CD.
Once this is done Grubb should load and ask you about installing, make sure when you are installing you choose your 80GB HDD and that you dont remove any windows (smb) hard disk partitions. Once you have defined the 80GB as the hard disk you want to use (depending on the version of SUSE) it will setup the partitions for use with linux automatically.
It will now ask you to setup the tools you want to install, if you are unfamiliar with Linux I'd suggest you go with the defaults (maybe selecting KDE and have this as your default interface). Follow the onscreen steps making sure that Grubb is setup to give you an option of booting windows or Linux (it should be default but worth checking).
Hope this is of use.
You might also want to take a look at:
SUSE INSTALLATION PAGE