Make sure you have a vista/recovery disc handy. Start up EasyBCD and uninstall the Vista bootloader. Verify that XP well boot. Then do a startup repair of Vista. Re-add XP's entry and if you are having problems after that post boot.ini and disk management screenshot.
So what did you do to get the Vista's to boot? Did you remember to put the 3 XP Files on the boot drive? Did you adjust the boot.ini file to represent the change from the boot drive to the XP Drive? Have you read the documentation troubleshooting area?
ok vista has always booted but NOT when ubuntu was connected to the sataII port . The problem was the lack of vista driver for that chipset > I still havent found one !!! I work round it by disabling the
sataII controller in the bios when i want to boot to vista > and re enabling it and choosing to boot from the disk list when i want to boot into ubuntu >which is a pain but easier than unplugging the ubuntu drive each time !!!..
as far as checking the wiki goes YEP I did for a change and i have added the ntldr file and the other to the boot root drive and it now boots to xp > which is great !!!! I did add the boot.ini file via note pad and then del it (i think!!!) as there was a message saying boot.ini was corrupt or summat on booting to xp . Despite del it I still get that message although it DOES go on to boot into xp ......