Hi,
Before moving on, I would like to explain it is normal that guest computer
can ping host computer if turning off firewall on host. It because Windows
Vista Firewall blocks ICMP by default.
Given the current situation, I have the following suggestions:
1. Please obtain IP/DNS address automatically to test the problem if
possible.
2. Please disable IPv6 on Windows Vista to test the problem. For detail
guide, please refer to KB929852 (
http://support.microsoft.com/kb/929852).
3. Please ensure Virtual Machine Network Service is enabled on LAN
connection setting.
Please understand that the Windows Vista works fine and the problem mainly
related to Windows XP settings in Virtual PC 2007, we do not familiar with
it. If the issue still persists after taking suggestions above, it is
recommended to post the issue on Virtual PC
newsgroup(microsoft.public.virtualpc). There is more qualified pool of
respondents who can give you suggestions. Meanwhile, other community
members who visit the newsgroups regularly can either share their knowledge
or learn from your interaction with us. Thank you for your understanding.
Hope it helps.
Robinson Zhang
Microsoft Online Technical Support