nw path not found error

iam having a problem with a small netwotk - one of the compputers cannot see any of the others and none of them can access it
the error message is -network path not found-contact your administrator.
the computer is on the network, in the same workgroup as the others and can access the internet
I can ping any of the other machines from it and vice versa. Have tried disabling Windows firewall but to no avail. all machines run winxp sp2
can anyone elp please