I received some email what i use, here's the dirty 2 second snippets:

for those who may like i have this that does the changes under linux:
(i called this executable script after sshing and going su)
#!/bin/sh
mount /floppy && cp --reply=yes /root/_spcbt/boot_xp.ini
/floppy/boot.ini && sync && umount /floppy

or you can do

mount /floppy && cp --reply=yes /floppy/boot_xp.ini /floppy/boot.ini
&& sync && umount /floppy

-just this one line of code suffices for it being called along with a
reboot cmd following it..i use sync just in case because i'm paranoid
and like to be sure it is written right away doesn't hurt
though...under xp, its no problem..i would prefer the 2nd way since
changes to the default location for either os can mean you can still
make system changes remotely and still be able to reboot into your
system if you hate looking for your default bootup config files
somewhere in the filesystem.

on my xp bootup: i make use of
xcopy /y boot_lin.ini a:\boot.ini (but again i can also use
a:\boot_lin.ini from the disk..) from a .bat file
then i issue an shutdown -r -t #numsecondsleft from a dosbox to
restart the system into linux..(i use a remote desktop program such as
rdesktop in linux or windows's remote desktop client from another
machine)

asher