It wasn't Mohammed who founded Islam.

[Rayaan]

I was hoping for something a bit more concrete... like which are unreliable and what do they claim that makes them unreliable, to you.
Remember that I'm mostly ignorant of Islam, so that would be a great opportunity to instruct me further.

They are unreliable when:
1. They contradict with a certain verse in the Quran.
2. If the hadiths have been classified as having a low grade of authenticity.

The authenticity of hadiths are strengthened by a sound chain of narration and by numerous, corroborating reports. The hadiths are an important part of preserving the teachings of Islam (in addition to the Quran).

Hadiths as a whole are accepted as true by mainstream Muslims, but not all of them are accepted as 100% true because there are varying degrees of authenticity depending on the number of narrators, the isnad, meaning, translation, logical consistency, and other aspects of the hadiths. Therefore, the early scholars of Islam developed a way of classifying the hadiths according to their level of authenticity. And there are a vast amount of literature and Islamic books on the scholarly science of hadith classification. Here are some links to get you started:

https://asimiqbal2nd.files.wordpress.com...hassan.pdf

http://www.islamic-awareness.org/Hadith/...ences.html

http://en.wikipedia.org/wiki/Sahih_al-Bu...thenticity

There is evidence of tribal societies in that area.
There is evidence that all the tribes became united under the rule of someone towards the end of the 1st millennium.
Something happened in there, more or less at that time. Call it what you will, I don't care much.
Starting with Abd-Al-Malik, there should be far more evidence of everything... isn't there?

You completely (and I believe intentionally) evaded the question which has nothing to do with evidence of tribal societies nor what Abd-Al-Malik did. Again, I'll re-phrase the same question, which is:

Do you believe that the oral traditions and posthumous writings - which refer to Muhammad - are at least somewhat reliable since now you believe that he did exist?

I always thought there was only one prophet, Mo. And that's the one I meant.
The first "he" is Abd-Al-Malik, the guy who spread the religion on the peninsula.

So then your final opinion is this:

Muhammad was the only one Prophet at that time (per the oral traditions, at least) and Abd-Al-Malik only spread the religion, meaning that the religion itself was already established (elsewhere), by Prophet Muhammad. He did that by, according to your own words:
"He had to convince a lot of people that what they believed, prior to his establishment, was wrong and this new prophet [Muhammad] was the one true prophet."

Agree or not?

If you do agree, then you're basically saying the same thing as the oral traditions regarding the historical origin of Islam. So, what's new that you're trying to tell me?