Given that God created everything, who created God?

From: http://www.islambyquestions.net/

Prophet Muhammad predicted that this question would one day be raised as he correctly predicted a great many future events of importance. On one occasion he said:
A day will certainly come when some people will sit with their legs crossed and ask: ‘Given that God created everything, who created God?’ (Bukhari, ‘I‘tisam,’ 3).
Those who put such questions are generally atheists or inclined to atheism and seek to lead others astray also. The purpose of their question is possibly to avoid the responsibilities owed by us to the Creator; belief and worship. At best, the question is derived from the observation of (what are taken to be) ‘cause and effect’ relationships. Every circumstance can be thought of as an ‘effect’ and attributed to an antecedent circumstance or ‘cause’ which, in turn, is attributed to some circumstance antecedent to it, and so on. In the first place, it is obvi­ous to anyone who reasons objectively that the notion of ‘cause’ is only an hypothesis, it has no objective exis­tence: all that objectively exists is a particular, often (but not always) repeated sequence of circumstances. Secondly, if this hypothesis is applied to existence as a whole, we cannot find a creator of it because each creator must have a creator before that creator, in a never-ending chain. (In fact, the futile notion of a never-ending chain of creators was one of the arguments used by Mus­lim theologians to explain the necessity of believing in God.)
The Creator must be Self-Subsistent and One, without like or equal.
It is self-evident that the Creator must be Self-Subsistent and One, without like or equal. If any created being can be said to ‘cause’ anything, that capacity to ‘cause’ was itself created within that being. Thus, no being in the universe can be said to be self-existent; rather, it owes its existence to the Creator who alone is Self-Existent as well as Self-Subsistent. It follows from the fact that the Creator alone truly creates that for each and every being He has determined all possible ‘causes’ and ‘effects’, all things whatever that come before or after it. Therefore, we speak of God as the Sustainer, who holds and gives life to His Creation from first to last. All ‘causes’ have their beginning in Him, and all ‘effects’ find their ending in Him. In truth, created things are no more than so many ciphers or zeros which, no matter how many we put in a series, add up to nothing, unless a positive ‘one’ is placed before the series to give it value. In just this way, the creation could have no real existence, nor any value, except by God.
What we call ‘causes’ have no direct or independent influence in existence, no direct or independent ‘effects’. It may be that we need to speak of ‘causes and effects’ in order to understand how, in a short space and over a lit­tle period of time, some part of the Creation is made (by the Mercy of God) intelligible to us and available to us for our use. But even this but confirms our dependence upon God and our answerability before Him. It is not God who needs ‘causes and effects’ to create; rather it is we who need ‘causes and effects’ to understand what He has created. He alone is the First and the Last, the Eternal, the Initiator and the Determiner—and all our busy little efforts after cause and effect are but veils between ourselves and His Majesty.
Let us then affirm once more: He, God, is One; God, the Self-Subsistent, Eternally-Besought-of-All; He neither begets nor was begotten; and nothing whatever is like unto Him.