Let's say there are some people who never heard of Islam. For example, they are in the middle of the Amazon rain forests and do not have any means of communication with the larger world. Would they go to Heaven or Hell?
Anyone who has not received the Da`wah (Invitation to Islaam) in the life of this world and died ignorant of the truth will be tested on the Day of Resurrection, according to the most correct opinion maintained by scholars. If they succeed (by accepting the truth), they will be admitted into Paradise. But if they oppose the truth, they will be cast into Hellfire.
This applies to all people categorized as Ahl-ul-Fatrah who have not received Da`wah.
The proof of this is in the following verse:
17:15 ...And never would We punish until We sent a messenger..
Imaam Ahmad in his Musnad (16301) said:
Allaah's Messenger (sallallaahu 'alayhe wa sallam) said: "Four will have proofs (in their favor) on the Day of Standing: (1) A deaf man who could not hear anything; (2) a fool (who could not understand anything); (3) a feebly old man; and (4) a man who died in the fatrah (the period between prophets). As for the deaf man, then he will say: 'My Lord, Islaam came and I did not hear anything.' And as for the fool, then he will say, 'My Lord, Islaam came and the children were throwing dung at me.' And as for the feebly old man, then he will say, 'My Lord, Islaam came and I did not understand anything.' And as for the one who died in the fatrah (period between prophets), then he will say, 'My Lord, no messenger from you came to me.' So He (Allaah) will take oaths from them that they will obey Him (in what He is about to request from them), so it (an order) will be sent to them: 'Enter the Fire!' And verily by Him in whose Hand is my soul, if they entered it, it will be cool and soothing."
It has been authenticated by Shaykh Albaanee as well.
Even only hearing about Islam is not Enough. Do we investigate everything we hear by name? For example, we heard of Shamanism; how many of us actually made research on Shamanism in detail?
Just hearing "Islam" is not enough for being responsible. In western countries, people hear about Islam everyday from media, but they hear in a negative way. They hear a different, violent, bloody religion which is actually not Islam. If they become enemies of Islam, are they going to be responsible of their hatred?
Allah never says that he is going to punish people just after hearing Islam. He never says something like this:
You heard about Islam. Why didn't you research it? You deserved my punishment for your ignorance and laziness!
But, he says that he will say something like this:
قَالُوا أَوَلَمْ تَكُ تَأْتِيكُمْ رُسُلُكُم بِالْبَيِّنَاتِ قَالُوا بَلَى قَالُوا فَادْعُوا وَمَا دُعَاء الْكَافِرِينَ إِلَّا فِي ضَلَالٍ
They will say, "Did there not come to you your messengers with clear proofs?" They will say, "Yes." They will reply, "Then supplicate [yourselves], but the supplication of the disbelievers is not except in error."
Mumin/Ghafir 50 (40/50)
From another ayat:
وَلَقَدْ أَهْلَكْنَا الْقُرُونَ مِن قَبْلِكُمْ لَمَّا ظَلَمُواْ وَجَاءتْهُمْ رُسُلُهُم بِالْبَيِّنَاتِ وَمَا كَانُواْ لِيُؤْمِنُواْ كَذَلِكَ نَجْزِي الْقَوْمَ الْمُجْرِمِينَ
And We had already destroyed generations before you when they wronged, and their messengers had come to them with clear proofs, but they were not to believe. Thus do We recompense the criminal people
Yunus 13 (10/13)
لَمْ يَكُنِ الَّذِينَ كَفَرُوا مِنْ أَهْلِ الْكِتَابِ وَالْمُشْرِكِينَ مُنفَكِّينَ حَتَّى تَأْتِيَهُمُ الْبَيِّنَةُ
Those who disbelieved among the People of the Scripture and the polytheists were not to be parted [from misbelief] until there came to them clear evidence
Beyyine 1 (98/1)
حَقِيقٌ عَلَى أَن لاَّ أَقُولَ عَلَى اللّهِ إِلاَّ الْحَقَّ قَدْ جِئْتُكُم بِبَيِّنَةٍ مِّن رَّبِّكُمْ فَأَرْسِلْ مَعِيَ بَنِي إِسْرَائِيلَ
[Who is] obligated not to say about Allah except the truth. I have come to you with clear evidence from your Lord, so send with me the Children of Israel."
Araf 105 (7/105)
قَالَ يَا قَوْمِ أَرَأَيْتُمْ إِن كُنتُ عَلَى بَيِّنَةٍ مِّن رَّبِّيَ وَآتَانِي رَحْمَةً مِّنْ عِندِهِ فَعُمِّيَتْ عَلَيْكُمْ أَنُلْزِمُكُمُوهَا وَأَنتُمْ لَهَا كَارِهُونَ
He said, "O my people have you considered: if I should be upon clear evidence from my Lord while He has given me mercy from Himself but it has been made unapparent to you, should we force it upon you while you are averse to it?
Hud 28 (/28)
And so on...
The word is:
You can make a search on this word in Quran. Quran is full of this word. Investigate how it is used, and how much it is important. You will see that only the ones who see the clear evidence are to be responsible. Just hearing is not enough to make you responsible. Hearing in TV can make negative effect as it does in western countries. If you hear Islam from someone else, you hear as much as that person is able to explain to you. You need to see a clear evidence to be responsible of what you saw.
And We never punish until We have sent a Messenger (to give warning). [17:15]
If someone never hears about Islam , then it is safe to say that he will not go to hell,but Allah knows the best. But if someone hears about Islam and knows about it, than he chooses his own fate.
This is taken from http://www.turntoislam.com/forum/showthread.php?t=23631