Executive summary: No. You shouldn't trust them.

What you're seeing from PC-cillin is a message similar to the following:

Next time you see that, click on the "Network Neighborhood" icon on your own PC, and you'll be startled to see just about all of their computers accessible to you. Click on a few and while many will hopefully require a password or deny your access, all too many are wide open and within seconds you'll be browsing their file system and even accessing their own personal files, photographs, spreadsheets, email archives and more.

True confession: I once poked around on a hotel network as an experiment and within five minutes was viewing photo albums and identifying Quicken and even tax software data files on multiple laptops. I wrote about it on my blog, of course: hotel Internet connection dangers and paranoia as a healthy tech lifestyle.

The problem is that Microsoft Windows, by default, leaves that network connection open to other computers on the local area network. When you're at home or at work, it's a well defined environment and there's no reason not to do this, but when you connect to a public network like the convenient wifi at a local café or even the wired network at a hotel, you suddenly are exposed to a far more risky environment with other computer users who might be hackers (or wanna-be hackers), curious snoops, or who knows what...

Ordinarily I'm a reasonably trusting sort of chap, but when it comes to the data on my computer or laptop, I am highly suspicious of others because in this day and age you need to not only worry about their intentions but the viruses and other software they might have inadvertently gotten on their computers too, malware that could easily be checking every 60 seconds to find new computers on the local network to infect or destroy.

The first thing you should do, therefore, is to mark every one of these computers listed by PC-cillin as "not trusted". You should also turn on and leave on the firewall on your Windows computer and tighten down the security settings so that you aren't going to be a victim next time you decide to hop onto the network and check your email.

Here's a good place to start, from Microsoft: Understanding Windows Firewall, and Microsoft's Security Center, which is chock-a-block with useful (albeit sometimes confusing) information about improving the security of your computer.

Let's be safe out there! :-)