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It's usually on C:\Nexon\Combat Arms
Go to your combat arms folder...
Default installs are in C:\Nexon\Combat Arms.
You're not running 64bit so yeah.
It's usually under
C:\Nexon\Combat Arms
It looks like this
C:\Nexon\Combat Arms
Otherwise I think you can open the properties or the Combat Arms Icon you have already and set it to open Engine.exe
I saw a video on that