unable to change password

I have forgotten password of the system.I am having SCO Unixware 2.1.2.I am trying to change the password of the system by booting it with boot floopy.I edited the shadow file and made the password field blank.But I am not able to login.When I try to change the password of root or any id using passwd command,it asks me for passwords twice and it throws error 'Unexpected failure.Password file(s) unchanged'.If I make the password field blank in the shadow for any other id than root and if I try to login after that it throws error that password has expired and gives following error 'UX:passwd:ERROR:Permission denied'.

Please help me.If anyone can suggest how I can login to system without asking for password from console,that would be great.The system is not on network.

Thanks,
Girish

See Lost root password