Welcome back~

You'll want to check here for the newer PlayOnline Viewer for Vista/7/8. That should allow you to run the disk installs and go through the tedious update process. However, you can skip all that by visiting here. The Welcome Back campaign is beginning soon, and as such, they let you download the game in it's entirety, though you'll still need content IDs from a purchased expansion to access it beyond the free week.

Info on the return campaign is here.