The best way to uninstall Mandrake is to first use a Windows 98 or ME cd, then just start up the system with "BOOT FROM CDROM" active in BIOS. Select option 3, to boot without cdrom support.
At the a:\ prompt, type:
FDISK/MBR and press Enter
after that, boot with the SUSE cd and format the drive with Mandrake on it.
Hope it helps, that's the way I would do it.