Figured it out.
There are two methods that I found, depending on what you want.
If you just want to make a Baldur's Gate DVD, then you can just copy the contents of each of the five CDs into a folder, then make an .iso (or other burnable file) out of the files in that folder, then burn it. That should keep it so the Autorun.exe still works, and CD1 is detected (so you can start the game).
But if you want to add Tales onto the same DVD, that makes it a bit harder. First, you can't just dump all the files from the six CDs into one folder, like before, because the Tales files will overwrite some of the CD1 files. So you have to put them in their own folders, one for BG (like above), and one for Tales. The problem this creates is that now the Autorun.exe doesn't work for either game. You can leave it like that if you want, then you'll just have to navigate onto the DVD and run the Setup.exe directly.
I didn't want to do that, so I went looking for a way to make my own Autorun.exe that linked to both games. Since, as I said, I don't know how to code my own, and I couldn't figure out how to edit theirs, I had to find a program to do it for me. After some searching I found a program called AutoRunner which worked great. So I created my autorun menu in that with links to each games installers and the run command. Works great, you pop in the disk, and the menu pops up... Just one problem, once installed the games wouldn't run because they didn't detect the CD in the drive.
So I started playing around with the CDs a bit, trying to figure out which files the game looked for. Eventually I found out that all you need is a copy of the CD1 and CD6 folders in the root of the DVD to get past the startup protection (I don't even think it's meant to be protection, the game just looks for those folders so it can play the opening movie, and if it doesn't find it then it can't start. It's just not smart enough to look on the rest of the disk)
So, now it works wonderfully. Both games install from the Autorun menu, and both games start using the DVD. No more need to scratch up my original disks. [img]smile.gif[/img]
I installed it with a full install, so I'm not sure how the DVD will react when the game needs a new CD (for the non full install). While installing, I was prompted to insert the next CD, like normal, but all I had to do was hit enter to continue.
For anyone interested, here's a screen shot of my Autorun:
Link
When you mouse over the images they dim and display the black/orange text like the Tales menu. When you click on an image it goes directly to that games setup.exe, then the skull opens the default Tales autorun menu so you can start the game. The white box in the corner is from the program I used, because it's only the demo.
Then here's my file structure, if anyone is interested in making their own DVD:
Link
I didn't include the movies that play after you finish installing the game (Descent3 and Painscape) because they annoy me.