Since you cannot remove anything from a DVD, you'll need to copy the installer to your hard disk, remove the preflight section, and do the install. Here is how:
1. Copy everything from the MINDSTORMS disk to a folder on your hard drive (the desktop will do).
2. Open that folder and look under “Parts.”
3. Locate MindstormsUnivEdu.pkg or MindstormsUnivRet.pkg.
4. Right-click (control-click) and choose “Show Package Contents.”
5. Navigate into the Contents » Resources directory and delete the “preflight” file.
6. Close this package and run the meta-package (LEGOMindstormsEngRet.mpkg) from the desktop to install MINDSTORMS NXT.
This should do it.
Once you have finished you can remove the install folder.
