...without losing the editing I've done in the develop mode? I don't want to move them, just copy them.
In Lightroom, there is nothing like SAVE.
Once you are done with your editing, then you can simply Export those pics wherever you wanted.
You just have to select the items and hit EXPORT in Library Module and then follow the dialog box.
Actually, if you press Ctrl(or Cmd)/S Lightroom will write the changes to the files that are highlighted. Then those DNG files can be moved to another computer and the changes will remain. Or, if you have selected the option to write metadata changes to XMP, then the DNG files will automatically get updated whenever you make changes to them. And those changes will remain with the files when they are moved or copied to another computer.
That's one of the big benefits of the DNG format, Pixeltaker. All your LR edits can be stored directly inside the file.
LR is a database driven application, so the database is the first place it stores all your edits. LR can be told to also store the exact same information automatically inside your DNG files, but it's not configured for this out-of-the-box. To insure the edits are written into the files themselves, you can do one of three things:
If you have non-DNG RAW files, LR will instead save the changes into a sidecar XMP file, as the proprietary files created by the camera manufacturers do not have a space designated for logging your edits. This creates two files to manage while moving files around, so I much prefer DNG for simplicity.
Then you should save to xmp (which is embedded inside DNG, so you won't see in finder/explorer).
Just note that snapshots are part of xmp, so via this method you can even hand over multiple develop versions. Virtual copies are not part of xmp, for these you need to export and will get an additional file per virtual copy.
Which program do you plan to use to read the DNGs from the DVD?
If it cannot trul read DNG such as Irfanview, you should update the preview inside DNG first before saving to xmp, as it will access only this preview.
I do that regularly, too. Any one of the three methods I outlined above will work. You also have the option of using the "export as catalog" function, which will also bring over all the previews your laptop has already rendered. Personally I usually just keep it simple and move the files, though.
Actually, you should probably use option #3, saving the XMP data into the DNG file (automatically, so it's there). Be aware however that if you moved edited files onto another machine containing the SAME file (you over write it) then when you start that second copy of LR up you'll get a "data mismatch" symbol in the upper right corner of the thumbnail (LR will be informing you that the image was changed "externally" to itself). Clicking on it will give you the option to import the data from the DNG file into the database to get them in sync. The only problem is that you loose the history data shown in the develop module when you import the XMP. You don't loose the edits, just the history.
I'm pretty sure that if you export as a catalog with the files on machine 1, then import that catalog on machine 2 with the files, the history data will be properly displayed.
Another advantage to option #3 is that if your catalog ever corrupted, you'd still have the edits stored inside the files themselves.
As JS4653 points out, expect to tell LR to import medatata from the files if you're replacing the same images in another catalog. In this situation, if you accidentally told LR to overwrite the discrepancy with the settings from its database, you would wipe out the changes that came over with the files.