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#21
Can you post back a screenshot of your full Disk management drive map with listings, using Snipping Tool in Start menu and attaching file using paper clip in reply box.
It may be as simple as removing Vista HD, plugging it's cable into Win7 or setting Win7 HD as first HD to boot in BIOS (after DVD drive), then marking Win7 active while removing incorrectly-marked active from the data drive, then booting the Win7 DVD Repair console or Repair CD to run Startup Repair up to 3 separate times to write the MBR to Win7.
However this will remove the System MBR from XP so it will likely be cut out of the dual boot until it is added back in from Win7 using EasyBCD 2.0 beta.
Disk Management snip will help determine this for certain so we can give you the correct DISKPART commands to use from Win7 DVD/Repair CD.