You didn't say what router and settings you used. Not only can wifi be interfered with but if it's WEP or less then the hijacker or other person can wreck such havoc.
If the wifi is removed from the setup, then you have only one more thing to check and to try another PC.
I have Charter Cable internet & TV. My PC operates on Windows 7. Until 5-6 weeks ago, we had experienced few problems over the last 10 years. We are now experiencing regular internet disconnects (with no TV disruptions) & most of these problems occur between noon & 5:00 pm.
The following solutions have been attempted:
Replaced wireless router
Bypassed new router directly to modem/PC
Replaced cable line from house to modem
Installed amplifier in attic
Replaced cable drop line (from house to utility pole)
Line techs have made "adjustments" at pole 3-4 times & at
amplifier on main line in alley
When I run Windows diagnostics, the message states "DSN server unavailable". I suspect a problem with the main line in the alley or with the server.
Any suggestions or similar experiences?