I'm sorry, but your question is not understandable (at least not by me!).
You must supply valid information - about distro, what have you done, what are the errors etc.
I *think* your problem is a username/password issue, but then you have some problems "there after"? What do you mean with that?
Password "administrator"? Isn't that the username?
"linux OS 6.4" does not exist. (6.4 makes me believe you might mean CentOS but "enterprise"? Is it really RedHat Enterprise - that one costs money!)
So, what distro is it?
It is a VirtualBox guest, here you are clear - good!
Is this then a fresh install or older? Have you been able to login before?
Is there a problem after you've logged in?
Are you logging in to a shell (text terminal) or a GUI (= graphical)?
Are you logging in directly in VirtualBox or from network?
What is your VirtualBox host (the system where you installed VB & created this Linux)?
(English might not be your native language but that's true for most people here, including me, so don't let that hold you down! Just try to be precise, give detailed info, and I'm sure we can help.)