Thanks guys. Much appreciated insights!

All of the Ackerman Computing links (DMB2, Vertigo and 5 of the 6 soundtrack links) in the OP seem to be broken.

Yeah, I just let that domain expire...I thought I'd already updated the links lol.

Anyway, they're back up now :)

Thank you for creating this nice summary of how to make Descent Collection truly complete.

I was fixing my old backups of Descent 1&2 from 2007 and saw they were no good. For example Rebirth was version 0.50 and there was no Collection level content. I was already in process of sorting the extra content from original Collection CDs when I discovered you already had them sorted out. I couldn't just abandon what I've started so I used your example to finish my own Levels of the World pack. I got the unsorted levels from CD to your state, documenting every change as it becomes 1:1 copy of it, but with some improvements:
- added two missing broken levels (INTERIM, SEALS)
- separated 22 MP levels from SP levels
- added missing TXTs
- adjusted date attributes of all modified files to match ones from original CDs
- readme with changes to get from original CD levels to sorted state from 1st post
All that because I couldn't stop what I've started, plus I'm can be a bit of a stickler when it comes to details.

Would you mind I post download link here or should I PM you first for approval? I don't want to come off as disrespectful by posting my stuff here that's based of your work. Please let me know, I think you will like it.

Besides your LOTW help I also grabbed The Enemy Within which looks interesting to say the least and I wouldn't have known about it had you not written the post.

Dude, if you got Interim and Seals working, that's awesome!! Where did you find the files to make it happen?

By all means, post a link here, and I'll update the collection on the DMDB (Descent Mission Database), if that's alright with you :)

I downloaded Vertigo for D2. It plays fine but when I run the game with the Vertigo updates there is no sound. The sound worked just fine before I updated to Vertigo. What do I do?

Are you using Rebirth or DOSBox?

I'm using dosbox.

The issue seems to have been resolved. The sound works now. Not entirely sure what I did but I fixed it.

I've updated the link to Levels of the World with Nilex's fixes. Thanks so much for doing that Nilex!! (To correct my previous post though, for clarity, Interim and Seals are still not working, Nilex just added missing extra files and such).

To run Levels of the world missions, you put them in the main Descent folder or in Missions folder?

If you're using a source port, put them in the missions folder.

I know putting them in the main folder works (both with a source-port and with DOS), but I'm not sure if putting them in the missions folder in DOS works or not.

Just a (random) notice: Do not try to use Vertigo with Rebirth's -lowresfont option. It crashes during the briefing.

Several levels from lotw doesn't work.

Every level that uses rdl files crashes the game when i try to play them. Is there a fix and if so how do i do it.

The Rebirth developers don't seem to be active here. You should report this on their forum or their issue tracker. Which levels fail? What game are you trying to play? Were you in single player or multiplayer? What is the nature of the crash?