The folders that you need to remove, including the Expansion Model folders, are as follows.

For the 757:
FSX\Captain_Sim\757
FSX\SimObjects\Airplanes\CS_B757-200
FSX\SimObjects\Airplanes\CS_B757-200F
FSX\SimObjects\Airplanes\CS_B757-300

For the 767:
FSX\Captain_Sim\767
FSX\SimObjects\Airplanes\CS_B767-200
FSX\SimObjects\Airplanes\CS_B767-300
FSX\SimObjects\Airplanes\CS_B767-300F
FSX\SimObjects\Airplanes\CS_E-767_AWACS
FSX\SimObjects\Airplanes\CS_KC-767A

The bold blue text is the Base Pack folders, bold black text is the Expansion Model folders.

It could be worth considering doing a full uninstall. This includes cleaning the windows registry. KB #685 has all the details on how to do that. It also means you need to activate the products again, but that shouldn't be a problem.

Hope this helps.

Mark