NetBSD-current/i386 has now an own ID for its partition
in the MBR partition table.
The new ID is 169 decimal, A9 hex.

READ THIS IF YOU WANT YOUR NEXT KERNEL TO
ACCESS THE DISK!

A new kernel config option, "COMPAT_386BSD_MBRPART",
allows to use the old ID (165). The GENERIC config file
contains an example.
The bootloader has a similar compatibility option; it is enabled
per default in its Makefile for now.
Both bootloader and kernel will issue a warning if you use
the old ID.

The transition works as follows:
-build a new kernel with "option COMPAT_386BSD_MBRPART"
  and install it
-recompile the bootcode in arch/i386/stand/biosboot and install
  it on your disk ("installboot")
-reboot - the warnings should appear
-with "fdisk -u", change the partition ID from 165 to 169
-reboot again - no warnings anymore

best regards
Matthias