If you are re-installing windows formatting is not required, if you launch the Windows 7 Setup disk there should be partioning options, anyway wouldnt it be easier to use a Windows 7 recovery disk so you don't need to re-install, Back to your question buttons on a computer always go directly to the OS so there is a 50% Chance if you press that button a Application will launch asking you to select a drive, you can order a recovery disk from Lenovo (i think) from (US Phone No.) 1-800-426-7378 Also F11 at Startup Can do a factory reset. Personally I would get a Flash Drive for safe storage or get free cloud storage at Dropbox or DriveHQ which is much more safe than Hardware when i Googled what does the Lenovo G550 Recovery Button do i didnt get any result but i read through your devices manual The button is the Onekey Rescue Button (A App as i said earlier) also this will please you: You can use the Restore to factory default feature to restore the system partition (C drive)
back to the factory default, i.e., the state your computer was when you purchased it. Make
sure you back up any critical data stored on the system partition (C drive) to other media,
SUCH AS ANOTHER DISK PARTITION (Your D drive is another partition), CD/DVD discs or removable storage devices. So Your D drive IS safe.