Andersen normally carries a 20 yr warranty on most of their products, 100 series warranty is only 10 years, if that's what you really have. You should call them to find out, you'll need the info imprinted on the glass in one of the corners of the window. Each pane can be replaced too, if not under warranty, I had the double hung narrowline series (before the 200/400 series separation), you can order directly from Andersen and Home Depot can special order these for you if they're available. Steps to do this are pretty straightforward, I had to repair 2 panes about 9 months ago. I ordered from Home Depot since it was about 10-20% less than ordering from Andersen directly. I've seen ads in the local flyers about companies that fix seal leaks, but I've never gone this path before.
Here's the Andersen link and phone info:
Contact Us | Andersen Windows