Hello, I have a new PC running Windows 7 Pro SP1 and with a virtual XP machine installed. I also have 3 other PC's running XP Pro SP3. All 5 PC's are in the same workgroup The 3 PC's and the virtual machine are visible on the Win 7 network, and all except one of the physical machines can also be accessed. The "missing" physical machine, call it PC X, appears on the Win 7 network list, can ping and be pinged from Win 7 but cannot be accessed (" X is not accessible...etc). PC X can see and access everything except the Win 7 machine. On the virtual XP machine the whole network operates normally, including PC X. All the physical XP machines and the virtual XP machine can see and be accessed from each other. The network is cabled throughout. I have compared all the network and protocol settings on the XP machines and they appear to be identical (but since they use different network adapters, this cross check is imperfect). I have checked that RestrictAnonymous=0 in the registry of PC X. The only obvious difference is that PC X is using Kaspersky Pure AV/firewall, but I have tried disabling that at start-up and it makes no difference. I tried giving PC X a static IP address, and also temporarily disabling its computer browser, with no effect. Although there is an obvious workaround - just use the virtual PC networking on the Win 7 machine - it is unsatisfactory, so any help would be much appreciated.

Although you disable the Kaspersky program from startup, some of its services are will still be running. I suggest you temporarily remove Kaspersky. If the issue does not occur after you remove it, please consider to check the configurations for the Kaspersky.Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Thank you, that sounded very promising, but there is still no change. I removed Kaspersky from PC X using the Kaspersky removal tool and re-booted both it and the Win 7 machine a few times, but to no effect, the situation is as before.

How does it work if you access the computers each other by entering \\IPaddress? If you can access the other computers, you may open Network, and refresh the list and see if it can find the Windows XP computer. Also, have you disabled the firewall and antivirus on the Windows XP computer?Please remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Well, that was interesting. From the rogue XP PC, in "add network place", \\192.168.1.10 (the Win 7 IP address)\shared filename does not succeed. But in "search for computers", asking for 192.168.1.10 as the computer name does work, and the Win 7 shared files become accessible, opened from the "search for computers" results window. First time I've seen them from that PC! However the Win 7 computer does not get added to the list of workgroup computers, and remains inaccessible from "my network places", in contrast to files on any other XP PC that is "discovered" during "search for computers". In the other direction, I don't know, and can't find, the equivalent of "add network place" or "search for computers" in Win 7 Pro. Attempting "http:\\192.168.1.7" (the XP IP address) from IE 8 fails, but the subsequent troubleshooter produces this message: "Your computer appears to be correctly configured but the device or resource (192.168.1.7) is not responding". Further checking suggested that the XP machine was not set to allow incoming TCP/IP - but its network adapter settings do not differ from those on the other XP PC's, all of which are accessible from the Win 7 PC and all include TCP/IP. When I first tested after removing Kaspersky from the XP PC there was no AV installed and the Windows firewall was off. Currently it has AVG, and I have tried disabling that too. Thank you for your suggestion.

The problem is fixed at last, after countless attempts. In a forum called "Active Network Forums" (I am not a member), there was a suggestion about a similar, but not identical, problem, referring to Microsoft KB903267. This recommended removal of the registry entry DhcpNodeType. On those XP machines that worked normally, this parameter was either absent, or set to the value 4, or to the value 8. On the rogue machine it was set to 2. This link http://technet.microsoft.com/en-us/library/cc781175(WS.10).aspx explains the effect of the different settings and of deleting the key - to do with node types. Any value other than 2, or the absence of the key allows something called B-node access for name resolution. The value 2 only allows P-mode. Not that I pretend to understand this, but the overal logic makes some sort of sense. Thanks again for your earlier replies.