FSX and SDK re-install question

Hello all, So, the night before last I ran a defrag on my FSX drive. Last night I got home from work and went to fly but FS wouldn't start. I got a "Fatal Error" message. I pulled the logbook, no luck, the FSX.cfg, no luck, scenery.cfg, no luck. Then I tried a repair using the disc. After that I got a message stating that Flight Sim could not load some programs and I should run a repair or remove. Now I'll have to uninstall all my add-ons and FSX. I have the Deluxe edition so I have the SDK installed on my O/S and programs drive. My 2 questions are:1: I'm assuming I have to re-install the SDK as well. Is that correct?2: It's alright to have FSX on it's own drive and the SDK installed on the O/S drive isn't it? That's how I had it but I haven't needed to use the SDK since installing FSX on it's own drive.Thank you for any help anyone provides.Have a Great Day,KailFlightSimmer since 1987C2D E6850 3.0GHz 1333FSBXFX Nforce 680i LT SLI2x XFX 8800GT 512MB SLI'd4GB Crucial Ballistix PC6400 800MHzCreative SB Audigy2 ZSUltra Xfinity 600W SLI PSUSeagate 320GB SATA-3GB/S HD for O/SWD 160GB SATA 3GB/S HD for FSXWindows XP SP3 / FSX SP2 / FS9 SP1