Hiya Doc,
First, try syncing 1 song onto the SD card and see if it prompts you to sync afterwards.
If that does not work, then:
I think WMP adds a .xml after the first successful sync.
Take a look at
this screenshot (You have to zoom up)
I have included the file in the attachments (Sorry it's a .zip, I can only upload .zip here)
Just put the file on the root directory of your SD card.