If you're looking to stop the Islamic conquest, you'd probably have to go back to the 7th century and take care of the originals.
Even then we might still have a lot of problems. Maybe that part of the world would be giving Orthodox Christianity a bad name instead of giving Islam a bad name.
If I had the power I would like to change Islam in some cult where pigs are honoured as sacred beings (the only reason they're unclean to Abrahamic religions is because they were prone to having deadly flatworms, it was dangerous to eat at those times, unlike today; but Muslims, unlike Jews aren't even allowed to touch a pig).
Women neither should cover up and would be seen as equally-valued (but not equal, but they shouldn't be less, like is the case in Islam). Nudity would be no taboo. Extra-marital sex would be allowed. There would be no problems with homosexuality. Visual arts, as well as music would be no taboo in any variant of Islam. There would even be statues of Muhammad inside Mosques. Polygamy would go for both sides, women and men. In the 8th century there was a great shortage of men, so polygyny would be encouraged. If there was a shortage of women, polyandry should be encouraged.
I just wouldn't be able to be that influential, even if I knew the Quraish dialect Muhammad spoke. I neither could get close to Muhammad nor influence him nor take over his place, I'm sure of this. I wouldn't be that well in producing a poetic/prosaic mix the Qur'aan is. I am only picturing if I had the personal power of uniting the Arabs and spreading this newfound doctrine to the masses.
So Islam remains the misogynous, ******ing, sober and violent cult that has grown too big.
By the way, I notice that post-Reconquistal Spain had a lot in common with Islamic Spain. Even the Inquisition is said to come from Islamic culture. It also used to be normal in Castilian and Andalusian culture to demand of women to lock themselves up inside their homes, cover themselves up or get harassed, a.s.o. Back in those days Spain wasn't even seen as 'real European' by other Western powers. You can see these references in Don Quixote. I'm glad Spain became Christian, because these influences are certainly Islamic.
I'm not a huge fan of Christianity, but at least Christianity wasn't such a brake as Islam in regards to arts. Sure, Islam had its golden age, but it was merely scientific. Also because of Islam art hardly developed (except among peoples who weren't that well Islamised, like the Turks, and they learned a great deal from the Greeks).
I also know that women here weren't respected until deep in the Middle Ages (from disdained to protected) and actually also until Modern times (from protected to equally valued). Also Christianity had an issue with art for a while, but not ongoing as is the case with many current Muslims and practically in every century Islam is existing.
Islam is to me like Christianity and Judaism, but in many regards more primitive. I both like as dislike the fact that there's no real hierarchy. I like it because no person's will is seen as absolute. I dislike it because every nutter who knows some base about Islam can declare himself an expert and can spread extremism at a faster pace than in other religions. Especially when a group is kept poor extremism spreads like wildfire and the leading figures of these extremists know this and try to make or keep the situation as miserable as possible in order to 'win' souls.
Personally I wish Europe remained to its older pre-Christian roots, they were just as violent, yes, but more tolerant religiously and less exclusive. But of course, in Pagan culture women neither were respected. Well, they weren't in Greek and Roman cultures. I know they were in Celtic, I don't know about Germanic though.
Having sex with your ancestors. Would be cool having an identical brother or father or w/e.
