I've always aimed at "ngwen" although as a native English speaker I'm still not great at starting words with "ng" despite years of trying. It's more common in Australia than most western countries as a lot of Aboriginal words use it so we have it in place names, such as "Ngunawal" an area near Canberra. On TV (since we have a few celebrities named Nguyen) they just wuss out and tend to go with "Win"