Hello guys...! We use various OS such as Windows XP, Windows 7, Windows 8 in our office. In the beginning there's no networking problem, Windows XP can access to higher Windows, and Windows 7/8 can access Windows XP. Everything's fine until installing windows update MS17-010 on last Monday for more secure againts Ransomware outbreak. Windows Update we installed : 1. Windows XP : kb4012598 2. Windows 7 : kb4012212 and kb4012215 3. Windows 8 : kb4012213 and kb4012216 After installing the Windows update, these problems occur : 1. Windows XP cannot access Windows 7/8 through \\computername or \\ipnumber\foldername, cannot access file sharing and printer sharing Error message: "Windows cannot find [\\computername\] ....." 2. Windows 7/8 cannot access Windows XP through \\computername or \\ipnumber\foldername, cannot access file sharing and printer sharing a. Error message (when access updated XP) : diagnose : "The remote device or resource won't accept the connection" b. Error message (when access non-updated XP) : just usual "Windows cannot access [\\computername\]", no diagnose message. This is what I've got and done : 1. Ping computername or ipnumber from command prompt is no problem. Windows XP can ping Windows 7/8, vice versa. 2. Windows 7/8 that have not been installed windows update still can access any Windows XP 3. Any Windows XP still can access Windows 7/8 that have not been installed windows update. 4. Any Windows 7 can access any Windows 8, and vice versa. 5. Any same Windows can access each other (Windows XP to Windows XP, Windows 7 to Windows 7) 6. Windows 7: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\LanmanServer\Parameters I changed SMB1 value from 0 to1, but the value back to zero after restarting. 7. Windows 7 : Local Computer Policy > Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options > Network security: LAN Manager authentication level I changed value to "Send LM & NTLM responses", but still nothing changed. 8. Windows Firewall setting and workgroup name are nothing changed just like before installing update. I need many hands to solve this problem, thank you Yusuf.