XP/Vista Dual boot problem

Hi,
I’ve just purchased windows Vista Ultimate and installed it on my computer on a separate hard drive to my current XP installation. When i boot my computer the only option that comes up for dual boot is windows vista, i have tried using EasyBCD and VistaBootPRO and have been unable to get Vista to recognise XP. Have researched and tried many tutorials with no success.
Some info…
*XP was installed first.
*Both XP and Vista are OEM editions, and both run perfectly fine individually.
*Vista is installed on a 80Gb IDE HDD and XP is installed on a 500GB SATA HDD.

Any help would be appreciated, cheers.