sure its possible,, some are wav some are wma and some use an xbox codec that you can download from the usual place and install on your pc making it possible to listen to them.
the way to get them on your pc is the hard part which isnt hard at all,, you have to back up your game then if its on your xbox hard drive,, just ftp the music/sounds you want to your pc.
or ftp to your xbox dvd and copy them that way.
KOTOR was all wav or wma i forget,, so it was cool if you wanted to pull all the sound bites from the disk. for those star wars fans.
as for something like Test drive with cool music,, well all the music there has been around a while and easily found other places. i havent looked at GTA or VC yet so maybe they are wav or wma files too.
oops also some are zip file and xip files,, which opening xip files is as simple as getting the plug in.
( i believe xip is the right file extension.)