Passwords and user names

When I  go into wdtv and get source my computer is recognised,  I then click the tick to say ok then it asks me for a username and password.  I ignore this and go to the tick to say ok then it say invalid. 

What username and password do I  use here instead.  I can see two computers but cant get through to any without this username and password.

Can someone just give me straight forward and very simple directions as to what username and password and where do I find them as this is new to me

thanks so much

What version of firmware are you using?   What operating system on your PC?