Code:
boot=/dev/hda
map=/boot/map
install=/boot/boot.b
prompt
timeout=50
message=/boot/message
lba32
default=linux
image=/boot/vmlinuz-2.4.0-0.43.6
label=linux
initrd=/boot/initrd-2.4.0-0.43.6.img
read-only
root=/dev/hda5
other=/dev/hda1
label=dos
In the above code, the lines you need to worry about are setting a default to boot to (which is your linux) and then setting a timeout (50 ==> 5 seconds). After that it should autoboot linux...