Unable to connect to XP computers in Network Share

Hi, I have had this Network setup at my home for a while. There is one desktop, which has Windows XP Professional (we'll call this XPA, antivirus is MSE), connected to the router through an ethernet port, and three laptops, one with XP Media Center (we'll call this XPB, antivirus is McAfee configured to share files and printers) and two with 7 Professional and Home Premium (one is my own laptop, 7-A, antivirus is MSE, and other is 7-B, antivirus is McAfee configured to share files and printers). A few months ago, every computer was able to see each other easily through their names, and were able to share files and printers easily, even with the two 7 laptops having password protection. All of them were in the same Workgroup (called WORKGROUP), and the two 7 laptops were in the same Homegroup, sharing files through passwords).

Now, I came back home from college, and oddly find that my laptop (which is 7-A Professional with MSE) can't connect either XP computers when I type their name (coming up with the error code 0x80070035: The network path was not found), I can only connect when I type in their IP address. It's the same when I try to connect from the XP computers to my laptop. I can easily connect to 7-B though, and 7-B can easily connect to my laptop, XPA and XPB (and vice versa). I have no idea why this is happening now, since I haven't really fiddled around with the settings in college (other than installing some program that will let me connect to the university network). Don't know if this changes much, but I have a dual boot set up on my laptop, with XP being the second OS, and it can easily connect to the other three computers, and the other three computers can easily connect to it.

I know that this may not be a big deal, since I can still share through IP addresses, but it does get annoying when the IP address for the desktop with XP changes, since it has the main printer shared, and I have to reinstall it if it changes. Could a random reason be due to me using Windows Anytime Upgrade to upgrade my laptop from Home Premium to Professional, which somehow changed some firewall port settings?...

Disable the firewall temporarily as a test, see if it makes a difference.

I tried that out multiple times, laptop still can't connect to the XP laptops through their computer name, even with the firewall off on all computers.

Here's a bit of extra info, in the Network page, when I click on my laptop, it shows Network Location: Undefined network, but when I click on the other laptop (called 7-B in this topic) that can be seen, it has the actual name of the network. It also shows two Network infrastructures for some reason: Internet Gateway Device (Network location being Undefined network) and Residential Gateway (Network location being the actual name of the network). Here's a pic of it:

http://db.tt/vs6ofBKP

Then, when I go to the 7-B laptop, here's how the network page looks:

http://db.tt/EaX70uOB

As you can see, the weird part is that 7-B is shown as being in "Network", and 7-A is shown as being in the normal Network. Also, the XP computers are in an Undefined Network. I don't know if this is normal or not in Networks with mixed OS's.

Have a look at this. File Sharing Settings.pdf

Roderunner said:

Have a look at this. File Sharing Settings.pdf

The main problem is that I can't connect to the XP computers by their computer name. I can connect and share easily through their IP address though.

EDIT: I found out the problem! The node type was Peer-Peer, so, after fishing through the sevenforums, I found a way to change it to Hybrid, and now I can connect to the XP computer through its name instead of its IP address! I will do some more testing tomorrow, and hopefully it truly is fixed. Then I can rest easy.