This indicates an attack attempt against a Code Execution vulnerability in Microsoft Windows Media Player.
The vulnerability is cause by an error where Windows Media Player fails to properly handle command-line parameters. A remote attacker may be able to exploit this to execute arbitrary code on vulnerable systems.
Windows Server 2003
Windows Server 2008
Windows Server 2008 R2
System Compromise: Remote attackers can gain control of vulnerable systems.
Apply the most recent upgrade or patch from the vendor.