Americans who’ve never seen the name go into paroxysms trying to say “in-goo-yin” or “nig-yoon” (like that chick trying to pronounce “Nagheenanajar” on Office Space, heh). I’ve only ever heard an Anglicized version uttered by Vietnamese English-speakers before, who pronounce it simply as “win”.
Is it really pronounced “win” in Vietnam, though? I would think the initial ng would make it sound a little more interesting.
Back in the late 1980s, there was an actor named Dustin Nguyen on 21 Jump Street. Even though his IMDB page says his surname is pronounced “win”, I could swear I saw interviews with him at that time where he pronounced it more like “gwynn”.
That said, I’m very curious to learn about the authentic pronunciation. The city where I grew up (Green Bay) took in many Hmong boat people after the Vietnam War, and many of them were named Nguyen. I never did learn the correct pronunciation. 
We have a reporter on Global TV in Edmonton with that last name. I’ve never heard her pronounce her own name, but when she is introduced her name sounds to me something like “Nuyen” (i.e. the g is silent).
I used to work with a young lady by this name. It was a never-ending source of entertainment to count the various ways people tried to pronounce it. She said to just ignore the ‘g’ and the ‘y’ - e.g. Nuen. Sort of like “NuWin” but one syllable. This page has a recording of something that sounds pretty much like that and is alleged to be the authentic Vietnamese way of pronouncing it.
No, the “g” isn’t silent. The “Ng” represents the sound usually written as “ng” in English. The problem for English-speakers is that “ng” never appears at the start of words, so it feels unnatural there. (There’s a second problem, which is that the “uye” part is a vowel sound not found in English either.)
If you’re interested in this, the general term for this is ‘phonotactics’, which are the rules that govern how speakers of a given language are allowed to arrange phonemes. As you’ve seen, a very strongly-enforced rule of English phonotactics is ‘the /ng/ phoneme cannot begin a syllable’. People can have a hard time even hearing strings of phonemes that violate their language’s phonotactics, and are more-or-less hopeless at reproducing them.
This is a statement about phonology, which is the inventory of sounds native speakers regard as distinct from each other (swapping one phoneme for another will change the meaning of a word) and valid for use in the language.
Your"South" link file sounds like I remember it from when I was in South Vietnam many years ago.
There were a lot of Nguyen’s at my high school and it was always pronounced “new-win,” but said really fast so it often just sounded like “win.”
I knew one person who pronounced it “New one” and another who pronounced it “Gwen.” But both were born in the US.
i knew a girl who had Ng as her surname. supposed to be pronounced “wee” but… wasn’t.
Angie, the ungrateful engineer with an ongoing engagement in Inglewood, might suggest that “ng” covers more than one sound. 
So it’s not “ngu” followed by “yen”?
Was actress France Nuyen’s name really Nguyen?
I had a roommate in college with that name. We once spent several minutes going back and forth: I trying to pronounce it, he correcting me.
Obviously there’s a sound in there that just doesn’t register easily to English-only speakers.
That doesn’t contradict what I said. The sound [ŋ] is usually written “ng” in English. However, “ng” in English words can be pronounced in various other ways as well – one of which is [ŋg], as in a few of he words you gave.
Logically, “A is mostly B” does not mean that “B is always A”.
With respect, none of those have “ng”; un-grateful, on-going, en-gage, …
I believe the pronunciation requires pressing the tongue against the back of the palate.
She’s still alive and her name at birth was France Nguyen Van Nga
Heh, this is what I was going to mention, which is a syllable that is completely unpronounceable by non-Cantonese speaker. 
“wee” is not even close…
Sure, but when you wrote that the Ng in Nguyen represents the sound usually written as “ng” in English (emphasis added), that sounded like you were suggesting that there was only one sound written as “ng” in English, rather than at least three. And as a practical matter, it doesn’t really clarify the pronunciation of Nguyen unless one knows which English pronunciation of “ng” you’re referring to.
I’m just teasing with this pedantry, of course; I understood what you meant. But then, I already knew how to pronounce Nguyen. 
I don’t suppose you’re in England?