looked up "windows media player cannot" on support.microsoft.com and got his article describing what sounds like your problem on XP"
excerpt from article #326680 below
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CAUSE
This issue may occur if your Windows Media Library index file is corrupted.
RESOLUTION
NOTE: Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps.
To resolve this issue, create a new library index file:
Remove any audio CDs, and then close Windows Media Player.
Locate the following folder:
C:\Documents and Settings\All Users\Application Data\Microsoft\Media Index
By default, the \Application Data\ folder is hidden. See the "More Information" section of this article for instructions about how to show hidden folders.
Note In some cases the index file may be located in a different folder. If you do not find the index file at this location, or if this folder does not exist on your computer, click Start, click Search, and then search for the Wmplibrary_v_0_12.db file.
Right-click the Wmplibrary_v_0_12.db file, and then click Rename.
Type Wmplibrary_v_0_12.OLD to rename the file.
Insert an audio CD, and then start Windows Media Player if it does not start automatically.
Windows Media Player re-creates the library index file.
MORE INFORMATION
How to Show Hidden Files and Folders in Windows
NOTE: Because there are several versions of Microsoft Windows, the following steps may be different on your computer. If they are, see your product documentation to complete these steps.
Click Start, click Control Panel, and then double-click Folder Options.
Click View, click Advanced Options, and then click Show Hidden Files and Folders.
