Windows 7: new PC is not showing XP machines in network places

Hello,



I know this seems like a common problem that can be solved by a 5 minute google search, but it's not!

First I will describe my setup here, then the problem. If I miss anything please let me know.

We have a network with several computers, 2 running Windows XP SP3, 2 with Windows 7 and the new one that's making trouble, also Windows 7.

Nothing has been changed with the cables, routers etc, only one new computer.
Every other computer can see all the others, meaning all XP machines see the Windows 7, the ones running Windows 7 see the two XP machines. But the new PC can only see the other Windows 7 PCs and not the ones running XP.
So it cannot be the LLTD (Link-Layer Topology Discovery) problem. But just to be sure I installed the hotfix from microsoft, still doesn't work.

I can access the other computers by typing in their names or IP addresses in the address bar (\\computer1), but they don't show up in the network places. This wouldn't be a big problem, but I have a software that requires this feature to be installed. :/

I hope somebody has an idea.
Thanks