Lavasoft's Ad-Aware is 10 years old (doesn't time fly when you're having fun?)

They have now released an "Anniversary Edition" and you will doubtless be offered an update next time you use an older version.

Watch out! they will do their damnedest to sell you one of their commercial versions. The basic version is still free, however, just don't try to register it; that's for the commercial versions.

The major differences that I can see (for the free version) are:

1. Interactive protection
2. Automatic updates
3. Internet tracks eraser
4. Faster scanning with more options