I recently setup a dual boot with ubuntu and xp and encountered this issue:

When i started to system, i was expecting the boot menu to appear so that i can choose which OS to start,unfortunately it did not and went on to load xp directly.

Try this out to restore the grub(boot menu):

Note: Type these commands one at a time and hit enter after entering each command.

Boot using your live cd and then click Applications->Terminal and start typing commands

1) sudo grub

2) find /grub/boot/stage1

(This will return a location something like (hd number,number) ex: (hd0,1))

3) root (hd0,1)

4) setup(hd0)

5) exit

And the best step now, yeah you got it Reboot and when you reboot you should your menu to choose the OS to start.

**Original content taken from -

http://ubuntuforums.org/showthread.php?t=224351

and i have tried it twice it is fast,easy and effective.

Have fun

Rohan