It's part of the Norton Utilities. Cleans up bad Windows Registry entries. They don't have a good description of it on the Symantec web site. Hmmmm - from the Help file:
Norton WinDoctor is the safe and easy way to diagnose and repair the most common types of Windows problems. It checks all the information necessary for Windows to run properly. Plus it checks for components needed by programs that run under Windows.
Norton WinDoctor starts with a Wizard interface to let you choose the kinds of diagnostic tests you want to perform. After running the tests, Norton WinDoctor displays an easy-to-read report of the problems it has found. Problems are listed by problem type in the order of severity. You can choose to display the list sorted by name or status (whether they are fixed).
Norton WinDoctor lets you tailor the repair process to your own needs. You can specify which problems to fix and how to fix them. Or, you can let Norton WinDoctor fix all found problems automatically.
If you decide you don’t like a repair WinDoctor has made, you can undo it. To undo repairs you made in previous sessions, use Norton WinDoctor’s Repair History feature. Norton WinDoctor keeps Windows running at peak efficiency. This not only makes using your computer faster and easier, but also safer. By fixing errors that might otherwise lead to data loss, Norton WinDoctor protects your work.
Don't know why they don't have something like that on their web site. Basically, it scans the Registry and cleans up issues that it finds. This is generally A Good Thing.