NO, this keeps popping up time and again, from what I gather
Neil Armstrong is not and was never a Muslim, he lives in the
US and is a bit of a recluse, he occasionally lectures. 
Someone told me that he explicitly denied being a Muslim and
does not know how the rumour started.

It is sad that some Muslims make up stories that have a snowball
effect and sooner or later become a "fact" that Muslims boast
about can you imagine what impression we give to those who
know about Armstrong?