I have a Freeagent 300GB external drive hooked up to my WRT350N as a NAS. I backed up my mp3 library here and used to be able to play them from any computer (plays via WMP as a default). A couple of days ago it started to complain with the following message: "Windows Media Player cannot find the file. If you are trying to play, burn, or sync an item that is in your library, the item might point to a file that has been moved, renamed, or deleted." I tried to add the drive to the library, but I still get the same message when I try to play the file.
What's weird though is I previously disconnected and re-mapped this drive many times, and still I could play files. It only seems to happen if I use WMP to play the file, if I open it with Quicktime, the files work.
I also tried to hook up the Freeagent directly to the PC via USB, and I was able to play the files with WMP.
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Take a look at how your NAS is connected to your desktop over the network. I can only assume that there's something wrong that's causing WMP not to "see" your NAS properly.
What about opening individual mp3 files with WMP?
Because if you're using WMP's database to play/find your mp3 library, any filepath or drive letter change renders it useless.