FASA Games, Inc.

1) can willforce be used to disbelieve illusions?
2) to break a fear effect (like deaths head)?

Without double checking the text, I'm pretty sure the answer is no (EDIT: I was wrong, see others' answers below). Willforce's basic reason for being is to amp up magical effects, not for use in counter rolls. In the case of things like disbelief and fear, if the character can't overcome those with base willpower, then willforce would do nothing but amplify the failure (or that's how I'd play it out). The exception would be rolling effects of spells that would counter those kinds of things.

"enhancing his ability to resist magical effects"

Willforce can be used for "resistance". That is passive. Disbelieving is active, however.

can u give me an example of using willforce to resist a magical effect then?

Anytime you could roll Willpower to resist a magical effect, you can substitute Willforce for the effect test.

ok, so can it be used to break the effect of the pain spell? or fear effect from deaths head or terror?

Yes.