YaST can be used to uninstall the Linux boot loader and restore the MBR to the state it had prior to the installation of Linux. During the installation, YaST automatically creates a backup copy of the original MBR and restores it on request.
To uninstall GRUB, start the YaST boot loader module (System+Boot Loader Configuration). In the first dialog, select Reset+Restore MBR of Hard Disk and exit the dialog with Finish.
Reboot the system and you will get your old bootloader.