If you can't log in as root because the password is lost or shadow file is corrupt, try to get in using the following...
1. Get a bootable CD (Any Solaris 6 or 7) will do.
2. Boot from the CD.
3. Bring up a console in the installation mode.
4. Mount / file system from the hard drive.
5. Edit /etc/passwd or /etc/shadow to remove the encrypted password.
6. Restart machine and boot from hard drive.
7. Now login as root with a blank passwd.