Cannot boot second os

I used DD11 to re-size the volume on my vista laptop. I rebooted with the XP disc and installed XP. After the install I could not switch to Vista because of a corrupt MBR. I used the Vista CD to repair the MBR but now the XP os would not boot. The XP partition showed as a logical drive in DD so I converted it to a primary drive and set it to active then booted with the XP CD and used FIXMBR. After that OSS would not come up and neither OS would boot. I was able to repair the Vista MBR and get back into vista but not XP. What do I need to do to be able to boot either OS with OSS?

Regards

Jay