I have networked PCs before many times successfully, so this is not my first time trying to network PCs in a home environment. Though I’m wondering if Windows 8.1 is part of the problem. I would have thought that for sure, until one of the new laptops running W8.1 would not connect to any of the other three PCs/Laptops running W8.1. Yet these other three W8.1 PCs/Laptops CAN connect to this laptop. Then it gets a little more interesting: this same laptop that couldn’t connect to those three W8.1 PCs/Laptops, CAN connect to a Windows 7 desktop, and a XP Laptop, and those two can also connect back to it without issue. It’s almost like my network is divided in half, and only half can talk to each other. But then when I thought it couldn’t get any more interesting, I realized the first three W8.1 PCs/Laptops can talk to the others, it’s just that the others (W8.1 Laptop, W7 Desktop, XP Laptop) can’t talk back to them without getting the error, "Logon failure: unknown user name or bad password” even though the username and password are 100% correct. I don’t fully understand this error, because on the surface, it’s just WRONG! My username and password are correct, but it appears something somewhere is interfering or hijacking the authentication process. Three of the computers (laptops) are brand new, just purchased last week and setup this week. The HostPC is also fairly new, just purchased last month. I am not using a HomeGroup, and have removed all computers that were part of a HomeGroup. I have enabled file sharing and network discovery and enabled “Use user accounts and passwords to connect to other computers” on all PCs. I have DSL and am using the wireless modem provided by my ISP which has router functionality built into it. It is a Sagemcom Model: F@ST 1704N. All computers are connected wirelessly. Time is correct on all PCs. I cannot use Group Policy, since they're all Standard or Home edition. DHCP is enabled and all computers are on the same subnet, using the 192.168.254.x range of ip addresses. The six computers are as follows: (I figured this may make is easier to visualize the layout) HostPC: HP Desktop W8.1 PC Name: DrsBlend U/N: DrsBlend p/w: 123456 (not showing my real password) PC1: HP Laptop W8.1 PC Name: DrsBlend-1 U/N: DrsBlend P/W: 123456 PC2: HP Laptop W8.1 PC Name: DrsBlend-2 U/N: DrsBlend P/W: 123456 PC3: HP Laptop W8.1 PC Name: DrsBlend-3 U/N: DrsBlend P/W: 123456 PC4: HP Desktop W7 SP1 PC Name: DrsBlend-4 U/N: DrsBlend P/W: 123456 PC5: Dell Laptop XP SP3 PC Name: DrsBlend-5 U/N: DrsBlend P/W: 123456 Every PC stated above has the same user name and password and is logged-in with the username, DrsBlend and the password 123456. The "Logon failure: unknown user name or bad password” happens when trying to access HostPC, PC1, or PC2 from PC3, PC4, or PC5. The HostPC can see and connect to all the PCs, but only PC1 and PC2 can talk back or access the HostPC. It’s like the HostPC and PC1, and PC2 are in their own little clique, and can talk back and forth to each other. Those three PCs can also talk to PC3, PC4, and PC5 as well, but PC3, PC4, and PC5 cannot talk back to them (HostPC, PC1, PC2). Profile corruption? I would have entertained that thought, but the fact the first three PCs can access and talk to one another kind of defeats that idea, and the fact the PCs were just recently setup. Firewall? Disabled, and disabled TrendMicro with no change. With them on/off, the first three PCs can still talk to each other and the rest of the PCs. Anyone have any additional suggestions?