Sorry about talking too much, but i had this in another post previously which may clarify some things for you God willing:
Allaah Almighty says in the Qur'an:
And verily, We have sent among every Ummah (community, nation) a Messenger (proclaiming): "Worship Allah (Alone), and avoid (or keep away from) Taghut (all false deities, etc. i.e. do not worship Taghut besides Allah)." Then of them were some whom Allah guided and of them were some upon whom the straying was justified. So travel through the land and see what was the end of those who denied (the truth). [Qur'an 16:36]
We sent not a messenger except (to teach) in the language of his (own) people, in order to make (things) clear to them. Now Allah leaves straying those whom He pleases and guides whom He pleases: and He is Exalted in power, full of Wisdom. [14:4]
You'll see that those who were misguided was because they never wanted to come towards God, so their own sins and stubborness increased them in their misguidance. Anyone who turns away from God has chosen the path towards the darkness and away from God, whereas those who turn to God, if they are sincere - God will bring them closer towards Him, the Most Merciful. And the final destination is either paradise or hellfire.
Now these Prophets who went to other nations were ordered to convey the message to their people. So Noah came to his people, Moses came to his people, Jesus came to his people, all the prophets of the past came to their own people to call to the worship of Allaah alone, and not to associate partners with Him.
Islaam means submission, and all the true prophets of Allaah called their people to Islaam, submission to Allaah Almighty. Some people obeyed the messenger while others rejected the messenger. Those who rejected the messengers were destroyed by Allaah because they turned away from Allaah arrogantly when the clear signs had come to them. Even though these prophets were calling to the obedience of Allaah and His reward of paradise.
Now because these prophets had come to their people, Allaah gave some of the messenger's books or laws. So Moses was given the Torah, Jesus the Gospel (Injeel) etc. But what did these books call to? They called to the worship of Allaah, and His law.
This was on another thread:
First of all, we accept the previous scriptures [the Old Testament, the Gospel etc.] When these were sent down to the prophets, it was upto the nation to preserve it.
We know that from among them, there were some people who distorted them. Why was this? Because they wanted to follow their own whims and desires. For instance we know that there are so much copies of the Bible today, each with its own different interpretation. None of these are in the original language, and we know that if a scriptures not in its original language - then it's just a translation, its not the actual scripture. [Look at the bible, and ask yourself why you're using that specific version, why can't it just be that you get the original one? The reason for this is because the original doesn't remain. What does this mean? It mean's that you can't compare any of these versions to see what the original message sent down to Jesus was.]
Therefore, we as muslims do believe that the previous scriptures were revealed to the prophets of the earlier nations, however - these got distorted, even though it was upto these people to preserve the message which was sent to their prophet. And we can rightly say that it doesn't exist no more.
Due to the fact that these scriptures were distorted, and the people started worshipping others besides Allaah, and said things about Him which they shouldn't have said (i.e. we're God's children etc.) Allaah sent the message to the final prophet - Muhammad (peace be upon him.) Muhammad (peace be upon him) would come to confirm what was in the previous scriptures [calling to the worship of Allaah/God Alone without any associates] and this message would be for all of mankind (instead of just for the children of Isra'eel.) This message will be preserved by Allaah, and no-one is able to alter it by Allaah's Mercy. We know that till this day [since over 1400yrs ago] the Qur'an is still in arabic and is still preserved the same way it was over 1400yrs ago.
Why you may ask? Why did Allaah not preserve the message of the previous prophets, yet He preserves the message of Muhammad (peace be upon him)? The answer to this is simple. When Allaah sent a messenger to his people, it was upto the people to preserve the message, but they never had to spread it to different parts of the world. However, the message given to Muhammad (peace be upon him) was for the whole world, so Allaah has preserved it, but it is our duty to spread it to mankind. [If you feel this is wrong, you will find verses from the bible which claim Jesus (peace be upon him) being commanded to “Go to the lost sheep of the House of Israel!”
Whereas Muhammad (peace be upon him) is being told:
"Say: 'O mankind! I am sent unto you all, as the Messenger of Allah, to Whom belongs the dominion of the heavens and the earth."
If you use try reading the Qur'an, you may find things which you find confusing, or verses which you don't understand. You may even accidentally take the verses out of context, so i'd just like to point out that the Qur'an can't be interpreted to our own understanding, rather - it should be understood according to how the Messenger of Allaah, and his companions understood it, due to the fact that they lived it throughout their life.
Therefore you'll have to look at the sciences of tafseer to get a true understanding of the interpretation of the Qur'an. You can do that by visiting these sites insha'Allaah (God willing: )
We don't totally reject the previous scriptures, we believe that they were original once upon a time. Think of it this way, the Old Testament, the New Testament, and the Final Testament (the Qur'an.) The Final Testament confirms what was in the previous scriptures, yet whatever was fabricated/distorted in the previous scriptures has been refuted in the Qur'an/Final Testament, and the Authentic Sunnah [prophetic way/sayings etc.]
If you have any questions, please don't be afraid to ask. And Allaah Almighty knows best.
PS: Now that i've seen your post above, if you try reading in the Qur'an - you won't find much direct information on Muhammad (peace be upon him.) Infact if you look in the Qur'an, Jesus son of Mary (peace be upon them) is mentioned more times than Muhammad (peace be upon him) is mentioned. The word Muhammad is only mentioned 4 times, whereas the name of Jesus is mentioned much, much more than that.
The best way to study the life of Muhammad (peace be upon him) is through looking at his biography, which is recorded through the sciences of hadith, so it really happened. We believe in it due to solid facts, and also faith. One doesn't lack the other, rather they both are hand in hand - faith and real life. :)