To reimage using a stored image, boot the Windows 7 DVD Repair console or Repair CD, select Recover Using a System Image, let the imaging application detect the image stored on E drive (named only WindowsImageBackup), tell it to reimage the HD and 15 minutes later it will be done.
Keep your files backed up separately as the image will only include your files up to the time it was created. In some cases, if you are still able to access Windows 7, you can start the reimaging from Backup Center and have it save your files before restarting to reimage the HD.