Windows NT6.1 can not connect to win NT5.2

Source
Source 2

Your routers needs to be connected DIRECTLY to your main (desktop) computer, not through another device. I had mine going through a VOIP adapter. I removed this, and how it works.

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Probs sharing Vista/XP

I could get to the Windows XP Pro SP3 computer with my Windows 7 Pro laptop, but got the error message when trying to open the shared folder. Some of these guys are reporting the issue correctly and I believe they did everything right. My tip, which did solve the problem was to add a registry entry that will increase the IRPStackSize to 15. Turns out for me the issue had nothing to do with networking. You can look here to help you solve your issue and read about the solution:
http://www.dslreports.com/forum/r21292996-XP-Pro-irpstacksize-is-too-small

The article you linked to:
IMPORTANT: Type "IRPStackSize" exactly as it is displayed because the value name is case-sensitive
The article the Event Viewer links to:
Using Regedit on the win XP PCs, open the following registry key:
HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters\IrpStackSize
So should I be using IRP or Irp? 

 Use 20 as size!

IRPStacksize errors only occurred when trying to access Shares of a Computer (laptops). Not transferring, just accessing.
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Data Type: DWORD
Default: 0x4
Maximum: 0xC
Increasing this value requires some memory from the non-allocated memory pool, but the impact should not be noticeable.
NOTE: It is not always advisable to set the IRPStackSize value to its maximum of 12. Generally, you should start the value at 4 and work your way up, increasing the value by 1 each time. The problem may still occur if the value is too high
--
"Ah, women. They make the highs higher and the lows more frequent." - Friedrich Nietzsche
"'It's the law' is just an excuse for the unintelligent and unimaginative to remain that way" - Me

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Although the permissions were set to "everyone" you also have to go to the
security tab, click edit, click add, type everyone in the box, click apply 
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Try turning off "Password Protect Sharing" under Control Panel > Network and Sharing Center ... I tried that and haven't had any troubles since. Once that is turned off filesharing is basically the same as XP
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Adjust OneCare through the following steps and that seemed to solve his problem:
Windows Live OneCare -
Change OneCare Settinge -
Firewall connection tool -
Tick relevant options (Network discovery, file and print settings, etc) -
OK -
Advanced Settings -
Change file sharing from 'Do not share files and printers" -
OK -
OK 
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change the workgroup name on the Vista machine from "workgroup" to MSHOME. Theen create a password on Vista User Account. I went onto view network computers on my XP machine, and the laptop (Vista) was sat there waiting. double clicked it, entered the user name which was the user account name on the laptop, entered the password and it was done.
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Make sure that file sharing is on, password protect is off and a Private Network id defined via Network/Sharing center. I also had sharing set on both system's C-root drives plus applicable printers, dvd and external HDD.
To make it work:
1. Get into ms-explorer,
2. Right-click on the c-drive that you're trying to access..
3. select properties.
4. select Security tab
5. see if User Name 'everyone' is in the list of defined users.
6. If it isn't, add it to the list by selecting 'advanced',then 'edit' then 'add'.. just type in the word 'anyone' in the user box and click ok. It is now added with limited permissions. Select it again and this time select 'edit'... click on 'full control' for the everyone user.
7. If it was already there OR if you just did step #6 above, make sure you give user 'anyone' Full-Control via the dit option above.
Keep going... you're not finished......
8. Go into 'advanced' again and look for user 'anyone' select it for 'edit'. If you don't see it, go back to step #6...
9. Once found and when in 'edit', give user 'anyone' FULL-CONTROL' permissions.
10. You may be given a few 'cannot grant permission' messages, but just keep clicking ok until the process completes... a few minutes.
You should now be able to connect without errors.
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REINSTALL THE WIRELESS ADAPTER ON THE XP COMPUTER
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Probs sharing Seven/XP

Mark - Apr 3, 2010

On the windows 7 machine, go to the network and sharing center. Click on the "Advanced sharing settings".
Almost towards the bottom, there should be a "File Sharing Connections" section, which is probably defaulted to the 128-bit encryption. Change it to the 40 or 56 bit encryption and your XP machine should show up.

For sharing between Windows 7 and Windows XP you have to set your Windows 7 computer to the lower encryption setting before it will see the Windows XP computers on your network.

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by Gunnar in Sweden http://www.filmtuben.se/index.php
If you're using Windows Firewall, you can skip this section, because Windows Firewall automatically opens the correct ports for file and printer sharing when you turn on network discovery. If you're using another firewall, you must open these ports yourself so that your computer can find other computers and devices that have files or printers that you want to share.
To find other computers running Windows Vista, open these ports:
*UDP 3702
*TCP 5357
*TCP 5358
To find other computers running earlier versions of Windows, and to use file and printer sharing on any version of Windows, open these ports:
*UDP 137
*UDP 138
*TCP 139
To find network devices, open these ports:
*UDP 1900
*TCP 2869
http://windows.microsoft.com/...