network problem

my customer have a peer to peer connected to adsl router and 16 port switch hub. currently we have 11 workstation on the network and i am adding 2 more PC, my problem is, i always having problem connecting it in the network. the first PC i add is, they cannot see my on the workgroup but i can see them,i always have error message of i dont have permission to use the workgroup.

the second PC’s problem is i cannot connect in the network but i can access in the internet and also i cannot ping the IP address that i assign on the 2nd PC.

please help me on this as soon as possible becuase i am beginning pulling my hair on it. thanks in advance.