Hi
I'm not a Solaris system specialist (yet:) but I guess that you can i.e. :
- conect this disk to the other SUN instalation, mount root partition and delete password from /etc/shadow file, or
- try to boot you computer with some rescue cdrom and then mount root partition and delete password from /etc/shadow file (I'm not even sure if you can use "system rescue" cd for Linux - what kind of fs is used in your instalation?)
I'm sure there is a lot of solution for you trouble (without Solaris reinstalation) ...
Google is your friend.
Search it for <a href="http://www.google.com/search?hl=en&q=sola ris+root+password&btnG=Google+Search" target="_blank">solaris root password</a>.
You will need your installation CD, when you're ready to fix the issue.