I get asked all the time, "what's the difference between the normal 599CD courses and the seminars?"
Most of the general seminars (Word, Excel, Access, etc.) were recorded first, a long time ago before I had the 599CD courses available. They were recorded from "live" web seminars that I held before I started selling the pre-packaged 599CD tutorials.
PROS: The seminars cover a wide variety of topics in a relatively quick progression. I don't cover each topic in as much detail, but if you need a quick overview of Word or Excel, the seminars are good for this.
CONS: Again, not as much detail, plus the quality of the video is nowhere near as good as the regular 599CD courses. Again, they were recorded from live events, so there are some audio skipping and missed video frames here and there. Generally the quality is OK, but not as professional as the 599CD courses.
Do you need to buy the seminars if you already have purchased the 599CD courses? No. There is nothing new in the general seminars that's not covered in the regular 599CD courses.
EXCEPTION: The Web Database Seminar is a special seminar that I recorded fairly recently. It has real good quality, and was designed to cover a specific topic: building an web-connected database for your site.