This seems to be a problem with WMP. Just today i ended up having to change the priority to high. But there really isn't anything resource intensive going on. Sound seems to drop out and i have to reposition the track time to get the sound back. Putting WMP on high priority seems to alleviate the issue but there isn't anything else running in the background that would cause this issue.
Vista has a similar issue, at least when it comes to someone i know that still uses a Vista machine. But this is pretty baffling. I might have to adapt to iTunes because this issue is quite annoying. Happens to both my basic media desktop and my i7 gaming machine.
In all scenarios i have seen with this problem is due to 2 or more hard drives, either internal or external. I don't know if this contributes to the sudden freezing with WMP upon first loading.