Removed PC From NT Domain & Now Can’t Log On (Windows XP Pro, SP2)

I had two user accounts in the workgroup. I added pc to a network domain to update virus definition files. After cleaning the viruses, I removed the pc from the domain. I now am prompted to press ctrl/alt/del which I didn’t have to before adding it to a domain. Now the username that appears by default is the NT username used while on the domain. I enter the password for that username and still can’t log in. How do I log on with the workgroup user account before I joined the pc to a domain?