How do you tighten a loose driver side window on a 2001 xk8 convertible The front of the window is about one inch behind the back of the window when the door is opened?

Hmmm... this is a little complicated, and impossible to explain, so read these threads on jaguarforums.com and watch the videos embedded in the threads. This first one shows you how to remove the door panel. You have to copy and paste the text because links are apparently not allowed.

http://www.jaguarforums.com/forum/xk8-xkr-17/instructions-door-panel-removal-door-card-you-brits-faq-37325/

And this one shows you how to adjust the window:

http://www.jaguarforums.com/forum/xk8-xkr-17/how-adjust-Windows-eliminate-wind-noise-video-faq-50534/

Note: I don't show the front adjustment in the video, but if you read further down in the thread someone else explains it. And BE CAREFUL! Disconnect the battery. I almost chopped off a hand because the window came down unexpectedly with my hand inside of the door.