help with codecs please?

hi, I am new to this game, hope some one can help please. I downloaded a 143mb mpg XDVD from a
bitcomet site I only have small hard drive, i tired to play it on my WMP and got this message 'unregistered' i donot know which codec to use to play this i wanted to transfer it to a CDR. I tested it with GSPOT and it cannot render and i got this message from it ,unknown error -0x80040154' does this mean it is useless or do I need a special codec to work this, all my other mpgs are fine and work perfectly and I have transferred them to CDR which I can play on my DVD player I do not have a DVD-RW or DVD drive. Cheers, many thanks!!

Chances are the file is an mpeg-2 (as opposed to mpeg-1). Try using videolan or media player classic to play it. If you insist on playing it in windows media player you can get an mpeg-2 decoder like the elecard decoder or dvd software (those are usually pay).
media player classic: http://www.gabest.org
videolan: http://www.videolan.org