No. That is how i got my system Dual Booted.
Install XP. Use EasyBCD. Reinstall the boot loader. From within XP get all the details of your boot. Under the msconfig>Boot.ini tab.
Go into the EasyBCD setup and edit your boot loader. Add the XP details and you should be all set.
I make it sound easy cause it is. The only issue i had was both XP and Vista thought they were the C:\ drive which confused the EasyBCD application. Which i was still able to get around.