"Nevertheless I tell you the truth; It is expedient for you that I go away; for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you. And when he is come, he will reprove the world of sin, and of righteousness, and of judgement: Of sin, because they believe not in me; Of righteousness, because I go to my Father, and ye see me no more; Of judgment, because the prince of this world is judged. I have yet many things to say unto you, but ye cannot bear them now. Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatso ever he shall hear, [that] shall he speak: and he will shew you things to come. He shall glorify me: for he shall receive of mine, and shall shew [it] unto you."
While many Christians believe this prophecy is talking about the Holy Ghost, that conclusion is not logical when looking at scripture as a whole.
First, the Paraclete is typically translated as advocate, comforter, or spirit and in these verses of John, Jesus (pbuh) says that he must leave so the Comforter can come to them. In numerous other verses of the Bible, there are verses that are believed to be referencing the Holy Ghost such as:
Genesis 1:2 - And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.
Isaiah 63:11 - Then he remembered the days of old, Moses, and his people, saying, Where is he that brought them up out of the sea with the shepherd of his flock? where is he that put his holy Spirit within him?
Matthew 1:18 - Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost.
Especially with the last example, it is quite clear that the Holy Ghost is believed to be existent before Jesus (pbuh) left this world. In my judgement, Jesus (pbuh) was talking about someone else. Where else does he talk about this Comforter? Let's see...
John 14:16 - And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever;
"Another" Comforter is important here. Jesus (pbuh) is talking about someone similar to himself and Jesus (pbuh) also states that "he may abide with you for ever". What is the Muslim perspective on this? The life of Prophet Muhammad (pbuh) lives with us forever through the Sunnah (literally means "trodden path". Muslims use this to describe the way of life the Prophet showed us to follow) and the Qur'an that has been preserved since it was revealed.
Again going back to John 16:14, "He shall glorify me." Anyone who knows anything about Islam knows that Muslims hold Jesus (pbuh) in a very high regard and we give him credit for what he preached about himself. Jesus is mentioned in the Qur'an in the highest ranks of the prophets of God and in order to call yourself a Muslim, you must accept Jesus as a prophet, accept his miraculous birth and his miracles. Is there one other faith or prophet that fulfilled this requirement for this prophecy to be complete?
While there is so much more to say on the subject, I believe this gives enough reference to the given verses originally stated.