To begin with, I am not very computer savvy. I am an older person with an older computer and a 2003 Windows XP using Google Chrome for a browser. (If anyone is old enough to remember when Windows first came out, and remembers their hologram security seal with a baby touching a computer screen - that baby was my son.) I am widowed, and without resources for help with computer problems, so I would greatly appreciate some help. But you might have to explain things in common english!

We have a wireless router provided by AT&T with WPA2. I have had a suspicion for a while that a neighbor is a hacker. Recently, if I log onto my computer late at night, it tells me that I don't have an internet connection. When I check the wireless network, my network doesn't even appear. What appears is a network that I don't recognize with a 5 bar signal strength. If I refresh the network list, my network appears (with signal bars), then the bars disappear on the unknown network, and I get a connection.

This must mean that someone is hijacking my network, or hacking into my computer at night - right?