How to switch 2 operating system??

[tausif_buet]

i first installed windows 7 ultimate in one drive & windows xp(sp-3) in another drive.
i have two operating system now but it does not show any option to switch one another when it boots/starts at the beginging??so how to solve the problem??

 

[treefrog07]

Boot to your W7 install disc, when the screen shows "Install W7," choose the Repair option in the lower left side of the screen. It will repair the bootloader, so after the next POST you'll have the selection screen for WinXP and Windows 7.