The installation method uses an old ps-script for Windows 7 and it is not clear if it works 100% for Windows 8 Dev.Prev. as well.
What you can do is delete the existing entry for Windows 7 in the BCD and create a new one.
This can be done easy with Visual BCD Editor.
Download and install. Run it (eventually wait for .NET version to be downlaoded and installed on first run)
Select the entry for Windows 7 in tree view right-click and select "delete".
After entry for Win7 has been deleted right-click again in tree view and select "Create missing Windows loaders". This will create a new Windows 7 loader (and loaders for other installed Windows versions - XP, Vista if present). Change wording of entry using F2.
Reboot - select the new menu entry which should boot Windows 7.
If there are still problems your Windows 7 is messed up and should be repaired using recovery.
It is possible that automatic recovery does not fix all problems on first run - reboot and run it for not more than three times.
If still errors - reinstallation of Windows 7 can be considered.