I'm going to start by providing all of the basics. Computer Group "A" (Any Windows 7 PC, all running Professional), Computer Group "B" (Any Windows XP PC), and Computer Group "C" (Any Windows Vista PC) are all connected to the Internet and are on the same subnet. All computers from group B can ping all computers from group C, and vice versa. They also can communicate through windows file sharing with absolutely no problem. All computers from Group A absolutely will not see group B in the network list, and group A computers will not ping group B computers by host name. However, if I type in a known IP address for a computer in group B, this works fine. This same thing happens in reverse, (B to A). Basically what I have seen so far is that Windows 7 is having problems accessing network shares from other OS's. I have literally tried almost every suggestion I have found about Windows 7/Windows XP file sharing to no avail. I have network discovery turned on for the Windows 7 machines. I have file and printer sharing turned on for the Windows 7 machines. I have enabled sharing for devices that use 40 or 56 bit encryption on the Windows 7 machines. I have tried turning off password protected sharing on the Windows 7 machines. I have also enabled "Use user accounts and passwords to connect to other computers." On the XP machines, I have disabled Simple File Sharing. I have tried clearing DNS caches and ARP tables. I have tried using nslookup to find a machine, to no avail. In summary, file sharing works perfectly fine between XP and Vista machines. Windows 7 can access Vista machines. But Windows 7 cannot access XP machines. Thank you for your time and any help you have to offer.

Hi, According to your description, this issue can be cause by the DNS resolution problem. Please follow this link to share printer and files with Windows XP and Windows 7 first: http://www.howtogeek.com/howto/windows-7/share-files-and-printers-between-windows-7-and-xp/ Please Note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information. If this issue persists, you can try these steps below: · Run the following commands to see if it works: Ipconfig /renew · Register DNS via command: Ipconfig /registerdns · Manually configure the TCP/IP settings, navigate a static DNS IP address which is the IP address of the router. · Clear the Hosts file 1 Click the Start Button, type "%SystemRoot%\system32\drivers\etc" (without quotation marks) and press Enter. 2 Right-click on the file "Hosts" (without quotations) and choose Delete. 3 Click Continue to confirm the deletion and verify the administrator permission. · Temporally disable the firewall on your PC · Disable IPV6: 1 Click “Start” 2 Input “Network and Sharing Center” in Search box and press Enter 3 Click “Change adapter settings” on left pane 4 Right click “Local Area Connection” can click “Properties” 5 Remove the option of “Internet Protocol Version 6” 6 Click “OK” Hope it helps. Regards, Leo HuangPlease 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.