To debug this, use the Network Connections control panel to select a wired or wireless LAN adapter and open the Properties panel. Click on the Authentication tab and make sure that "Enable IEEE 802.1X Authentication for this network" is not checked. Repeat for all LAN adapters on your PC. If that makes your problem go away, great.
If not, using the Services control panel, stop the Wireless Zero Configuration service. Note that this will stop Windows XP from identifying and offering to connect to Available Wireless Networks, whether you use 802.1X or not. But it will also stop EAPOL.
I suspect that, at this point, you won't see the EOPOL problem any longer. You can see whether EAPOL is running by using new debug features in Windows XP SP2. Using a command window, enter "netsh ras set tracing * enabled" and try to view the EAPOL.LOG file in your system root Tracing folder (e.g., WINDOWSTracingEAPOL.LOG). If there's no EAPOL.LOG file when tracing is enabled, then EAPOL isn't running.
I'm guessing that, when you try to play an audio file, your Media Player tries to connect to the network -- for example, to retrieve media information from the Internet, acquire licenses for protected content, check for updates, or download codecs automatically. If that's happening, then perhaps your LAN connection with 802.1X accidentally enabled tries to authenticate via EAPOL but can't, locking things up. You might want to check your Media Player Options panel for any settings that use Internet connections. Many programs have a nasty habit of using the Internet to "phone home" by default, but you can often turn those features off by fiddling with privacy options.
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