The tool to use here is free Partition Wizard bootable CD
Back up your files and if desired a Windows 7 Backup image as Resizing operations can fail, although none have so far helping 100+ here extract Dual Boots.
Boot CD,wait for file loading, select 1 for screen res.
Now rightclick on 100mb>Delete to make sure it is deleted, OK.
Next Rightclick on Windows 7 to Resize, dragging left grey border all the way to the left over deleted 100mb. OK.
Make sure Windows 7 is still marked Active or Modify>Set to Active, OK. Now apply all steps.
Windows 7 will not now start. Instead boot the Windows 7 DVD, select Repair on second screen, click through to Recovery Tools list to run Startup Repair up to 3 separate times with reboots to repair the MBR and start Windows 7.