If I understand correctly, you choose among 4 drives at boot and "Drive 0" will successfully boot Windows XP. Rather than the MBR, this sounds like a problem with the GRUB boot loader configuration.
First, take a moment to learn how to configure GRUB (see, for example, this page
). You might want to print out a sample grub.conf file. This will be helpful in the next steps.
Reboot, and then when asked which drive to boot, highlight your SUSE Linux option and press "e". This will let you view and edit the GRUB boot configuration for that option (the interface for editing is rather unusual, but it will display some help text on screen). Any changes you make will only apply to the current boot; changes are not saved. Edit the configuration, and when you are done, press "b" to try to boot.
If you boot successfully:
Remember the configuration that you used to boot - you now need to make your boot configuration change permanent. If you don't know, figure out which partition is your boot partition, where GRUB is located. Then fix your (boot partition)/grub/grub.conf (you may need to mount the boot partition first). Reboot and verify that your new configuration is working.
If you don't boot successfully:
Reboot and try again. If you still can't figure it out, here is what can do. First, boot with that handy Knoppix CD. Figure out which partition is your boot partition, where GRUB is located (you may need to mount it first). Open your GRUB configuration file, (boot partition)/grub/grub.conf, and write it out on a piece of paper. Then, come back to this forum and please post your grub.conf.