Cool. Nice to know  I tried what I said about using v7 and in PT7 works perfectly the same exercise. Witchcraft jajajaja 

After doing some reserch, I'm sure that is a problem of PTC 8. All thanks to a comment at a Youtube video. We have to try at PTC 7  "I discovered you cannot use the newest version of Packet Tracer (8) with this lesson. The username and password do n...

I'm stuck too. I'd tried admin/admin, cisco/cisco, admin/cisco, even admin and no pass, but it says that must be pass. 