Hey..just to share so that if anyone else faces can check this solution that worked for me, I also faced the exact same issue but got it resolved by below activity.
> Get the Administrator password from Domain Controller
> Get in the system where you want to install.
> Goto "Groups" and open Administrator
> Add DOMAIN\Administrator in that group and restart the installation from scratch with the mentioned string.
> Also if you want can add the same account in SAP_SID_GlobalAdmin & SAP_SID_LocalAdmin groups too.
So when I added the domain admin as Admin in my host I was allowed to continue with the installation again.
My Env - SWPM10SP6 - Windows 2012 Domain Controller - Windows 2008 Host system
