Perhaps more details are needed. Who created the virtual lab? Is it associated with a course? If so, which course? Did you receive instructions with the class? The instructions will also typically include the username and password, even if they are supposed to be filled in.
As a suggestion, if this is related to a SAS class, try typing an s in the username field and see if a suggested username and password popup that will fill in the rest.
Dan Obermiller