It should only have one entry per song in the library as shown on your hard drive,have you moved any music around?
Whilst in wmp,find the 3 or 4 tracks right click on each track >properties and note each location c:my music etc.
If they are in 3 to 4 different locations that will explain it.
If not, do all entries play?they may just need a re index.
to re index the wmp library