It is possible to activate an inbuilt cheat menu, if, like for me, the trainer cannot find the game.
I'm not entitrely sure how I did it, but a simple Google search for cheats for Serious Sam HD The First Encounter is where I think I got it.
"Cheat menus
While in gameplay press ~ key to activate the console. Type "cht_bEnableCheats=1" (without the quotes) to enable the first set of cheats options such as Max Health, All Guns, Level Selection, kill all enemies. After entering this command press ~ then ESC and then F1 you should now have the cheat menu. From now on at the bottom of the menu (Load,Save Options,Leaderboards...) you should be able to see Cheats F3, this is the cheats menu. Type "cht_bEnableCheats=2" (without the quotes) to enable second set of cheats options God Mode, Ghost, Invisible and Fly mode. After entering this command press ~ then ESC and then F1 you should now have the cheat menu. From now on at the bottom of the menu (Load,Save Options,Leaderboards...) you should be able to see Cheats F3, this is the cheats menu.
Code: Result:
cht_bEnableCheats=2 God Mode, Ghost, Invisible and Fly mode
cht_bEnableCheats=1 Max Health, All Guns, Level Selection, Kill all enemies "
As I said, I'm not 100% certain as I tried different things and the line might be"sam_iEnableCheats=1"
If you use that and succeed you get a message saying your scores do not count on any leader board. Which is fair.
Hope this helps while we wait for the trainer to work.
david