Although you really need the 727-100 Base Pack (csp721_2400.exe) to go with your 727-200 Expansion Model (csp722_2400.exe), there might be a way to get the textures to display.

Navigate to FSX\SimObjects\Airplanes\CS_B727-200\texture.xx (xx is equal to something like aircanada (texture.aircanada)) and open the texture.cfg file with notepad. It should show this:

[fltsim]
fallback.1=..\texture
fallback.2=..\texture\spec
fallback.3=..\..\CS_B727-100\texture
fallback.4=..\..\CS_B727-100\texture\bump
fallback.5=..\..\CS_B727-100\texture\night
fallback.6=..\..\CS_B727-100\texture\spec

As you can see, it is looking for the textures in the CS_B727-100 folder, but your folder is either a different name (I don't own the 727-100 Exterior, so I don't know), or the texture that ARE in the CS_B727-100 folder it is looking for are named differently and so it still can't find the ones it needs.

I hope you can follow what I mean. ;)