Hello, I installed Windows 7 on a separate drive from Windows XP. On booting the computer the two operating systems appear but I cannot used the arrow or tab key etc to select the operating system. It defaults to Windows 7 after 30 seconds.
check out the guide here:
http://www.howtogeek.com/howto/8790/dual-boot-your-pre-installed-windows-7-computer-with-xp/
this may help you...!
Best of Luck