… is quite easy if you know what to do (and it’s update safe!):
Will be / Is DEPRECATED. Please refer to: http://www.triggers-world.de/?p=249
Only precondition: win7 or any other OS you want to boot as default is the next OS after the standard debian entries in the grub list / win7 is the only other OS installed
1. Edit /etc/default/grub
#find&edit or add if it doesn't exist
GRUB_DEFAULT=`/bin/bash "/somedir/getlastboot.sh"`
2. in /somedir/ create a getlastboot.sh with the following content
#!/bin/bash
VAR1=`ls -l /boot | grep -v .bak | grep -c initrd.img`
VAR2=`ls -l /boot | grep -v .bak | grep -c vmlinuz`
let DEFAULTX=VAR1+VAR2
echo $DEFAULTX
3. make it executable
chmod 777 getlastboot.sh
4. update-grub
sudo update-grub
(I have not tested it on ubuntu, but it should work there too)