rIGHT.New to all this. have loaded all three games, MW-TRIB-BLMOON. Playing from start. rest Charater at one stage, Dark brotherhood sneaks up and then I get messages saying cannotload run executables, how do I fix?

Maybe you must reinstal the game?
I had the same problem.
al my topics like:
- background
- morrowind lore
- little advice
- little secret
are destoyed to!!!!!
so I diciced to reinstal the game, but don't delete your saved game.
when i reinstal it i had no problems anymore.

In plain english- just try re-installing.