Standard CDA DisksI'm assuming you want to create a standard audio CD that can be played in any CD player (home, auto, etc.) or see below for mp3 CDs.
If this is so, the burner (disk recording application) must be able to write in standard CDA format (the audio is in PCM). It must also be able to convert whatever your source file encoding is to this format. Most files are stored as WAV, mp3 or wma formats. To do this conversion you must have CODECS (compression/decompression programs) installed, usually in DLL (dynamic link library) form, that handle your specific formats. Most burner applications come equiped with all the normally needed CODECS and do the conversions and writing seamlessly.
Occassionally the CODECS can be corrupted, sometimes when updating/upgrading or reinstalling an application. Your WM burner for example. I would retry the update or restore your system to a previous known working date. If this doesn't fix your problem, make sure your options in your WM burner are set to write CD's (default) unless you are trying to make mp3 disks.
Burning mp3 CDs in Windows Media Player: WM 9 does not normally include the CODECS for burning mp3s. They can be purchased from MS. WM 10 includes these CODECS. Update to the latter if you want to burn mp3s.
Options for setting the defaults can be found under the Burn Tab, right-click on Tools, left-click on Options.
Hope this helps!
BTW: I still recommend using something else for your burner application (NERO, Roxio, etc.). Big Bill may not approve of what you're doing someday, then you'll be stuck with whatever he forces you to do.
Dell