how to choose dual boot option for window 7 & window xp/vista

If u firstly installed a fresh copy of window 7 & after that u want to instal window xp in another logical drive. all will done easily but after instalation of xp, u will c that their is no option to boot the window 7. even for the choise of operation system u will see that their is only option of one operating system ie window xp. Now what to do to boot the window 7 again. here is the easiest tweak
*Put the dvd of window 7 into ur drive
*select option boot from cd
*then select rapair window 7
*thats it, it will just take 1 minute
*and u will get again boot of ur window 7