I must be doing something wrong, because my Taxi lights on the 737-800 do not work, is there a bug in the game or just me? Iam talkingabout the plane that is build into the game.

It isn't you. There are all kinds of things that don't work properly in the default planes. Internal/external lighting is a big problem. Especially in the 737 and 320. SP1 didn't fix any of them.

I took a bash at fixing the left and right inboard landing light switches which appeared to be reversed from what they should be doing.The fix worked great and can been seen here on AVSIM at FSX forum post 393678, "FSX Boeing 737-800 appears to have a bug - but it can b..."(The fix required editing the related XML file)You may wish to try out the fix - I mention it here so as to give any interested parties ideas that might help.