I was told that Islam is a Christian heresy closely linked with the Arian heresy, that denied the divinity of our Lord Jesus Christ. It is obvious that from reading the Qu'ran and the sayings of the "Prophet" that he had some what of an imperfect knowledge of Christianity.
If you look at Islam and her prayers and traditions you can often see what seems to be perverted Christianity.
One time I was at a mosque during Ramadan and was listening to a man, I asume he was the Imam, chanting verses from the Qu'ran. I was shocked when I realized how similar his chanting was to the chanting I hear at Divine Liturgy. It seemed too much like byzantine chant, it was quite scary.
Also Muslims, pray five times a day, as you mentioned. Praying at fixed times during the day is not of Islamic orgin but rather of Jewish and eventually Christian origin.
It might also be pointed out that Muslims postrate when they pray, once again postrations find their roots in ancient Judasim and of course Orthodox Christianity.
I think it is hard to read the Qu'ran and study the customs and rituals of Islam without seeing a hint of Chirstianity and Judaism. However it is obvious that Islam is a long way from being anything Chirstian, but I do think it is true that Islam finds its origins in Christian heresy.
As far as the prayers said during salat here is a link.....http://www.as-sabereen.com/dosalat.htm
After looking over the prayers, I do not think these prayers are based upon Christian prayers, however not all of the prayers directly contradict Christian teaching.