Microsoft has ceased development of WMP/Mac and is now offering a free version of Flip4Mac called
Windows Media Components for Quicktime. This plugin redirects Windows media to Quicktime and I have found that media opens in a Quicktime player within a browser window. If the Windows media file or stream requires WMP 10 codecs or is protected, then you still will not be able to view it. Microsoft, especially, has stated that protected media will never be viewable in anything other than Windows.
I do not know if the Windows Media Components is available as a universal binary yet. One of the problems you are probably encountering with Windows Media Player is that it is not a universal binary so you would need to force Safari to run under Rosetta for it to see WMP. You do this by control-clicking on the Safari icon and choosing Get Info. You would then choose the Rosetta option and close the Get Info box. Safari will run slower under Rosetta.