I think on SP1 and Sp2 does not have "Engine Stress causes Damage",either way it doesn't matter, also I seem to remember Lewis or Scott mentioning awhile back that box is not neccessary to have checked anyway for Accu-Sim to work properly.
You can download Sp1 and SP2 at http://www.fsinsider.com
go to downloads these are directly from Microsoft so safe,just ignore if it pulls up Microsoft Flight/click on downloads and you will see FSX downloads.or just open up FSX while on the internet go to "Home" and it will pull up the same website.
Is this just the Boeing 377 aircraft only? windows Vista/windows 7 "right click,run as administrator" on all the install's, also I think it will ask you if you have Acceleration or SP2 installed and you select the right one,not sure about the latter statement with just the aircraft.
Hope this help's