If you want to boot from grub separate windows 7 and windows xp do the following

Boot from GParted Live cd and make primary partitions.

/dev/sda1 Windows XP hidden flag
/dev/sda2 Windows 7 boot flag
/dev/sda3 Ubuntu

1.Install Windows 7 on /dev/sda2

2.Boot GParted live cd again, unhide /dev/sda1
and sed boot flag to it, hide /dev/sda2

3.Install Windows XP on /dev/sda1

4.Boot GParted live cd and unhide /dev/sda2


5.Install Ubuntu on /dev/sda3