It is unable to find windows xp boot data.
Solution can be simple, just fix windows boot by "windows recovery", it is done by booting windows installation cd and then goto recovery mode and then run command.. fixmbr and fixboot
It will over write your grub, now you need to restore grub, for that now run Linux LIVE CD, any live cd like ubuntu and then run command
grub-install /dev/hda
It will restore grub and you should be now able to boot both OS.
Above solution is simplest one and works always.