Yeah Carlo is correct about the VGA female/female adapter... Typically you'll only need this if your monitor has the VGA cable hardwired. If your monitor simply has a VGA socket (like most LCDs, HDTVs or Projectors) then the Xbox VGA adapter should plug right in.
As for audio, All of the Xbox cables terminate into male Stereo RCA. And most PC speakers are looking to plug into a Female 1/8" stereo jack.
So you'll need one of these:
Plug it directly into your Speakers. If your speakers happen to have the male 1/8" jack hard wired then you'll need a Female/Female 1/8" stereo coupler in addition to the cable above:
Make sure it's a "STEREO" coupler and NOT a "PHONO" coupler, a phono coupler will transform the Xbox audio into a mono signal... which is probably something you don't want to do