Hi Shardash,
thanks for your suggestions but unfortunately it didn't help.
I have tried to reinstall the VMWare tool on the Windows 7 guest system.
Besides, the VM already had the E1000 network adapter.
Furthermore I have found out followings:
on the Win7 i do ping www.google.com -t
It works until I start the windows XP Mode, then www.google.com is not reachable.
After windows xp mode is started I do the diagnose wizard on the network adapter of win7.
The network connection is alive again. My ping works..
If I then do ping from xp mode, it doesn't work. Host is unareachable, even if the XP Mode also gets an IP Address from the DHCP server.
Then I start again the diagnose wizard from Win7. As usual, I can then ping www.google.com again from the win7.
As soon as I try to ping www.google.com from the XP Mode, the network connection on the win7 is gone again.
Besides, I still can't ping from my XP Mode.
I am also very curios, why can't I find any difference in ipconfig /all on the Win7 before and after I do the diagnose wizard ?
The diagnose wizard result is always "Default Gateway not Available".
Thanks