Some readers are reluctant to upgrade or replace vulnerable Windows 7 PCs, even though Microsoft no longer provides security updates for them.

Instead, the readers are searching for technical tricks that would allow them to keep using the Windows 7 PCs while isolating them from other computers on a network. While that sounds good, it’s not practical.

Michael Kehoe, of Minneapolis, asked how he could isolate a vulnerable Windows 7 PC on his home network (see tinyurl.com/y5on8xko ). I said that it was possible to do that (using a Wi-Fi network technology called a subnet), but that it was technically challenging for consumers.

But reader Bill Fuhrmann, of Brooklyn Park, Minn., suggested another way Kehoe might isolate his Windows 7 PC on a home Wi-Fi network. Rather than set up a subnet, Fuhrmann said, why not put the Windows 7 PC on a secondary “guest Wi-Fi network,” a feature provided with some newer wireless routers (see tinyurl.com/y4ahn44a and tinyurl.com/y5g6on2s ).

Such routers simultaneously run two Wi-Fi networks, one for your personal use and the other for your guests. Supposedly, these two networks can never connect to each other. So, if you let friends use the guest network, any malware lurking on their phones or computers can’t infect the computers on your personal Wi-Fi network. Likewise, if you put poorly protected devices — such as some wristband fitness trackers, smartwatches or voice-activated music speakers — on the guest network, their security flaws can’t imperil your personal network.

But what if the guest and personal networks really aren’t separate from each other? Some researchers claim that it’s possible for hackers to first take over your guest Wi-Fi network, then use that foothold to steal data from your personal network by using “cross-router data leaks” (see tinyurl.com/y4cyw94r CQ).

The researchers said the best solution is to use separate wireless routers for personal and guest networks. But that would add cost and complexity of running a guest Wi-Fi network.

My opinion: Windows 7 isn’t safe for consumers to use, and simple Wi-Fi networking tricks aren’t likely to make up for that. If you have a Windows 7 PC, upgrade or replace it.

Question: My Windows 8.1 PC, an HP Pavilion 20, has become very slow. I ran several cleaning and anti-malware programs, ran diagnostic software and deleted some temporary files, but those things didn’t help. I also checked the hard drive, which has plenty of space. The Windows Task Manager shows that the Microsoft Internet Explorer 11 browser is using more than 60 % of my processor time and RAM (computer chip) memory capacity. Do I need more RAM memory? — D.B., Beardsley, Minn.

Answer: You should replace Internet Explorer 11, an older web browser that’s prone to slowdowns. Microsoft still provides technical support for IE 11, but no improvements. Try the free Google Chrome, Mozilla Firefox or Microsoft Edge browsers, all of which are being updated regularly. Edge initially only worked on Windows 10, but a Windows 8.1 version is now available.

Adding RAM might make your PC run a little faster for some tasks, such as Web browsing. But its probably not worth adding RAM to a seven-year-old PC that’s nearing the end of its useful life. You would be better off putting the money toward a new computer.