and where should i put the 'default' tag?
So in grub.lst the default value is 0 which refers to the first stanza. So if your XP partition is 3rd in order change the line to "default=2".

## ## End Default Options ##
title Ubuntu, kernel 2.6.20-15-generic
root (hd0,8)
kernel /boot/vmlinuz-2.6.20-15-generic root=UUID=4a45f168-015f-4b98-9160-754632ca7bf4 ro quiet splash
initrd /boot/initrd.img-2.6.20-15-generic
quiet
savedefault
title Ubuntu, kernel 2.6.20-15-generic (recovery mode)
root (hd0,8)
kernel /boot/vmlinuz-2.6.20-15-generic root=UUID=4a45f168-015f-4b98-9160-754632ca7bf4 ro single
initrd /boot/initrd.img-2.6.20-15-generic
title Ubuntu, memtest86+
root (hd0,8)
kernel /boot/memtest86+.bin
quiet
### END DEBIAN AUTOMAGIC KERNELS LIST
# This is a divider, added to separate the menu items below from the Debian
# ones.
title Other operating systems:
root
# This entry automatically added by the Debian installer for a non-linux OS
# on /dev/hda1
title Microsoft Windows XP Professional
root (hd0,0)
savedefault
makeactive
chainloader +1
$ dpkg -L rtorrent
/.
/usr
/usr/bin
/usr/bin/rtorrent
/usr/share
/usr/share/man
/usr/share/man/man1
/usr/share/man/man1/rtorrent.1.gz
/usr/share/doc
/usr/share/doc/rtorrent
/usr/share/doc/rtorrent/README
/usr/share/doc/rtorrent/TODO
/usr/share/doc/rtorrent/copyright
/usr/share/doc/rtorrent/examples
[B]/usr/share/doc/rtorrent/examples/rtorrent.rc[/B]
/usr/share/doc/rtorrent/changelog.Debian.gz
$ dpkg -L rtorrent
/.
/usr
/usr/bin
/usr/bin/rtorrent
/usr/share
/usr/share/man
/usr/share/man/man1
/usr/share/man/man1/rtorrent.1.gz
/usr/share/doc
/usr/share/doc/rtorrent
/usr/share/doc/rtorrent/README
/usr/share/doc/rtorrent/TODO
/usr/share/doc/rtorrent/copyright
/usr/share/doc/rtorrent/examples
[B]/usr/share/doc/rtorrent/examples/rtorrent.rc[/B]
/usr/share/doc/rtorrent/changelog.Debian.gz
download_rate = 70
upload_rate = 23
directory = /tmp
session = ~/.rtorrent/session
port_range = 453-459
download_rate = 70
upload_rate = 23
directory = /tmp
session = ~/.rtorrent/session
port_range = 453-459