Two drives it is!! My last comment would be to put FSX and all FSX add-ons(nothing else) on the 1 Tb drive and w7, MS Office and anything else on the SSD. FSX will be happier with it's own home.

A direct quote from Nick Needham -

HARD DRIVE TIPS FOR HIGH PERFORMANCE (ALL DRIVE TYPES):

- WHEN SSD SPACE IS LIMITED DUE TO ADDON SPACE CONSUMPTION, USE THE LARGEST MECHANICAL DISK PLATTER DRIVE FOR A DEDICATED FSX INSTALL

- DO NOT INSTALL LARGE DATABASE ADDONS (REX-GEX-FEX-AS2012, ETC) TO THE FSX DRIVE OR WINDOWS, POINT THEM TO A 'DEAD STORAGE' DRIVE **

- WHEN EVER POSSIBLE, USE SATA CLASS SSD -OR- PCIE STORAGE CONTROLLERS FOR THE BEST DISK PERFORMANCE WITH FSX

- RUN FSX AND PRIMARY ADDONS THAT REQUIRE INSTALLATION DIRECTLY INTO FSX ON ITS OWN DEDICATED HARD DRIVE

- INSTALL LARGE PHOTOSCENERY DATABASES TO THEIR OWN DEDICATED HARD DRIVE(S) AND POINT FSX TO IT

- MULTIPLE DISK SYSTEMS ARE FAR BETTER AND ALLOW MORE OPTIONS THAN SINGLE

- DON'T FALL FOR THE "HYBRID MECHANICAL DRIVE" OR 'CACHE' MARKETING GAME

- YOUR SATA CABLES MUST BE RATED FOR THE PORT AND DRIVE SPEED

- PSU MUST BE RATED WITH A LARGE NUMBER OF DISKS

- THERE IS NO SUCH THING AS 'TOO MANY' DISKS

- RAID IS NONSENSE AND A WASTE