If you can boot into 7,
install EasyBCD 2.0 after doing quick registration to use beta. Remove any XP entry in Add/Remove and then Add it back. Accept offer for boot files, Save.
If this will not correct Dual Boot, post back a screenshot of your full Disk Mgmt drive map using Snipping Tool in Start menu, attach file using paper clip in reply box. Add a snip of your Easy listings page.
If you cannot boot Windows 7 yet or the above fails, Try using EasyBCD2.0 in XP to Add 7 after removing it if necc. in Add/Remove tab. You'll need to install Net Framework 2.0 to use it in XP.
If this fails, boot into Windows 7 DVD Repair console, click through to Recov Tools list to run Startup Repair up to three separate times with reboots. If Windows 7 still will not start, return to Recov Tools list, open a Command prompt to type:
DISKPART
LIST DISK
SELECT DISK # (for Windows 7 HD)
LIST PARTITION
SELECT PARTITION # (For Windows 7 partition)
ACTIVE
EXIT
Now return to tools list and run Startup Repair up to 3 separate times with reboots to write the MBR to Windows 7 to start it, then use Step 1 above, posting back screenshot if necc.