I accidently downloaded a CRJ-200 texture from American Flight Avation, and didnt know it was a 200, and now all my CRJ-700's are gone from my FSX aircraft selection menu. I even uninstalled the CRJ-200 texture.

It's probably due to faulty fltsim.x entries in your aircraft.cfg file for your CRJ-700They should look something like this:

[fltsim.0]title=Bombardier CRJ 700 Paint1sim=Bombardier_CRJ_700model=panel=sound=texture=1kb_checklists=BombardierCRJ700_checkkb_reference=BombardierCRJ700_refatc_id=NCRJ70atc_parking_types=GATE,RAMPatc_airline=Orbitui_manufacturer="Bombardier"ui_type="CRJ700"ui_variation="Orbit Airlines"ui_typerole="Regional Jet"ui_createdby="Microsoft Corporation"description="The CRJ (Canadair Regional Jet) family of aircraft was derived from the Canadair Challenger business jet, which began its operational life as the LearStar 600. The Bombardier Canadair CRJ700, which entered service in 2001, is a stretched version of the CRJ100/200 regional jet, with increased seating capacity from 50 to 70. With increased length and upgraded landing gear, the CRJ700 features a longer wing span and leading edge slats. Like other members of the CRJ family, the CRJ700 features an electronic flight instrument system (EFIS) avionics suite and

Wrong: you probably forgot to make a backup of the previous aircraft.cfg. Usually wrong numbers only makes the textures disappear. What I mean is that the livery won't appear on the aircraft selection menu, as the texture's order is considered invalid after skipping or duplicating a number. While panel and sound.cfg files may immediately be installed, aircraft.cfg files require backups incase the original one causes problems. Without one, FSX won't be able to retrieve the aircraft whenever an error is caused, and so the plane is hereby deactivated due to a lack of a backup to return the original setup before the aircraft.cfg was modified. You should also check whether the lines of each [fltsim.x] entry are similar.