Good Evening,

Since I got my new notebook with Vista I've got trouble ever since.
I recently posted a bluetooth issue but this time I have a rather more important problem.
Somehow, my notebook is not able to connect to/ be accessed from any other computer on the network (not even himself).

Once again, I will use screenshots to illustrate my problem:

http://smg.photobucket.com/albums/v237/Iceblizzz/?action=view&current=FullNetworkMap.jpg
Here you can see the 'full network map'. The first pc is the notebook that's causing me the headaches (Vista Home Premium).
Second is an other pc on the network (XP SP2) and the last is an other Vista notebook (Vista Business).
There are several other computers on the network but, since they weren't turned on, they weren't visible.
The first thing that is bothering me is why i can't click on the second pc's icon (XP SP2). Is this because it's not running on Vista? (And yes, the LLTD protocol is installed on it, so Vista should be able to detect and access it).

Also, in the 'network' window I can only see the 2 Vista PC's:
http://smg.photobucket.com/albums/v237/Iceblizzz/?action=view&current=VistaNetwork.jpg

But when I try to select any of these two (as I said before, due to one way or another, I'm not able to connect to the XP one) it starts loading for a while and suddenly comes up with this error:
http://smg.photobucket.com/albums/v237/Iceblizzz/?action=view&current=CannotconnectNetwork.jpg
And this error occured when I tryed to connect to my own computer on the network (so connect to himself).
When diagnosing the problem it says:

Cannot communicate with (pc-name) on IP: xxxx
The remote host was pinged but there was no responce.

And sometimes:
Windows cannot find the hostname (pc-name) using DNS
The DNS may be down

When pinging in command prompt, it also shows:
REQUEST TIMED OUT

But... when pinging to the XP device, it shows the following error:
Reply from xxxx : DESTINATION HOST UNREACHABLE
Reply from xxxx : DESTINATION HOST UNREACHABLE
" ..............     "

I got a symatec (norton) firewall running and all computers are on the same workgroup (mshome).
I hope to hear from an expert.