[Guy Harris <guy@xxxxxxxxxx>]

> Thanks Alex,
>     I tried some other programs too (Network Associates' Sniffer 
> Basic).They show up the same way too. 
>     I see all the broadcast packets and the multicast ones but no TCP. 

Then the problem is almost certainly what Alex Bennee described - you're
probably on a switch or switching hub.

Some switches/switching hubs support "port mirroring", which means that
can be configured to send copies of *all* traffic going through the
switch to a particular port, so that you can do promiscuous traffic
capture on that port.  You'd have to check the documentation for your
switch to see if your switch supports it, and, if it does, to see how to
switch it on.