well that was all my fault.
actually i was creating an veterancy system with special items, which grant some bonuses.
so for example a shaman after 300 seconds of battle, if he manages to survive, gains an item named Badge of Wisdom, which increases it's health and mana by 200, damage by 12 and mana regen by 25%. every unit have a 4 slot inventory, and units can't sell, buy, drop or pick up any items. so the only thing in what they spend their slots are the veterancy badges. so a shaman may have 4 badges of wisdom, if he manages to survive for 1200 seconds (20 min which is pretty much for a standard unit).
however the problem is that even if i set the values of (can be dropped after death to false) here and there, after the shaman dies and decays the badges appear on the place of his corpse.
i was struggling with the problem, and I've asked about that in Russian forums, and they told me that it's impossible to get rid of the dropped item even with triggers. and someone advised that i should remove the item after some amount of time after death.
so the idea was if the shaman dies and decays and the badges are dropped, then after 30 seconds ('cuz some idiot told me that that is the minimal time in triggers) to remove the item from the ground.
well after struggling with the triggers a bit longer i've managed to remove the items from units just in the time of their death.
well, anyways, thanks alot for your aid =) and really sorry for the confusion i've caused.
it's due to the fact that i was told that it's impossible.