Not to sure if this will work or not, but worth a shot.

- Insert first CD in for BC
- Whatever window comes up just x out of it (close it)
- open My Computer
- open the drive where the BC CD is
- locate the file autorun.exe, or setup.exe
- right click the file and select to run as an administrator

Proceed as normal. At 98% my guess is that is trying to write some shortcuts to a common folder and like you said it doesn't have permissions.

And by the way, I am running Vista 64