SQL Server 2005 and SSPI Context on XP

I have an XP box with SQL 2k working without any problems. I am trying to install SQL 2005 CTP April on the same machine. Installation goes fine, but when I try to connect, I am getting an error "Can not Create SSPI Context". Why am getting this error ? DOes the machine needs to be on a domain to get connected? If yes, is there a work around? Can I use mixed mode? Where\How do I specify password for sa?
Any help is highly appreciated.
Thanks
_GJK

[473 byte] By [GJK] at [2007-12-16]