> when you install grub IMHO it places it's code on first disk block
> overwriting netbsd booter.

On which partition do you use "installboot"? If you use e.g. /dev/rwd0d it
will place the bootcode at the start of the disk, but if you use /dev/rwd0a
(or wherever your NetBSD root partition is), it should not install something
outside of that.


Martin