Please try to scan the Table of Contents to spot the topic of your interest. Video encoding is one of the last great frontiers where PCs can never be fast enough.This is a long article. If you plan to encode video a lot, either be very patient, or buy the fastest P4 or Athlon system you can afford. The only reason to go with DivX is if you have a standalone device that understands the DivX MPEG4 format. Like Steve, I can't recommend the Nero Ultra suite highly enough. That enables Nero Digital playback in WMP on my box.
No need to install every codec under the sun, unless you want to just deselect everything except for the 3ivx video and sound decoders.
As an alternative, you can download the full version of the K-Lite Codec Pack. Windows Registry Editor Version Type"="video/mp4" As Steve helpfully pointed out, you can pay $7 for the 3ivx decoder which- with a small registry modification- enables playback of *.mp4 files in good old Windows Media Player: Unfortunately, Nero hasn't seen fit to distribute a standalone "Nero Digital" decoder, which is not exactly a great way to promote a new file format. We should be able to download a small set of decoders and watch our *.mp4 files in any application we want.
Anyway, the upshot of all this is that you're forced to install the annoying Nero Showtime application on any PC you want to watch your *.mp4 files from.
AAC is a part of the MPEG4 spec, but it's not widely used. It defaults to multi-channel AAC encoded sound instead of your typical (less sophisticated) Dolby Digital or MP3 encoded sound. Nero calls their format "Nero Digital", but it's really just advanced MPEG4. All of the above packages technically produce MPEG4 output, but no DivX compatible decoder I found- and I tried many- could deal with the Nero Recode file format. MPEG4 video files, with a *.mp4 extension. Now, there is one thing you should know about Nero Recode: it produces somewhat. If you want a fuller overview of the Nero Recode software, there's a good review at CDRInfo. Ripping to MPEG4 is what I'm most interested in, but Recode can do much more.
I've long considered Nero the definitive DVD and CD burning software I had no idea they also offered a DVD ripping solution. Steve Makofsky turned me on to some software I already use: Nero Burning ROM, but more specifically, Nero Recode 2, which is a part of their expanded "ultra" Nero suite.