"Add to Library" Search Doesn't Add New Songs

I have about 1,750 songs on my computer in the My Music directory (separated
out by artist, album, etc). I usually add songs a few dozen at a time and use
the "Add to Library by Searching Computer" feature to add the songs to the
library. However, the last time I placed songs in the My Music folder and
tried to add them to the WMP10 library, only about half of the songs actually
entered into the library. Every time I use the "Add to Library by Searching
Computer" feature it says that it's added 1,200 new songs even though that
can't be right.

This was working just last week and I don't know what's happened to it! The
only changes I've made to my computer, however, has been to install the
Windows Updates that my computer had been annoying me about for some time!

How can I get my playlist to get back to normal?

Thanks in advance for your help and happy new year!

 

In truth a lot of people have had trouble with this feature. The files
may suddenly all show up in a day or two. Are the relevant folders being
monitored by WMP (see Tools > Options >Library)?

 

I'm actually not using the Monitoring Tool at all. All I'm using is the
search feature that runs through the My Music folder and is supposed to add
all the audio files to my library. I don't use the monitoring tool as it has
almost never worked for me.