Binos
Put the Tiger CD in, open it and double click install.
The Mac will restart, firing up from the CD.
You should then be able to access 'Disk Utility' from the menu bar.
Click on erase and do a 'write 0's' erase from the options - this will be enough to ensure that the average new user will have no access to anything on your disk.
When complete you will have a virgin blank disk to continue the install.
When asked for addresses etc, just type in ***** and leave the password blank.
Regards
N