This mainly happens when your OS is trying to update or send data to the data center and installed software is downloading or uploading data in the background. Also, it can be the hard disk is probably just too old. You can replace an old hard drive. In fact, it’s recommended before lagging is replaced by the blue screen of death. A new hard disk drive won’t cost a lot of money. Also, it can be that you touched a notification that popped up on your computer and it downloaded a virus which you have to go to a tech to fix if you dont have anti virus protector. And if it keeps going that means it can overheat or just breakdown and never work again.
Remember the question says LEAST LIKELY. The questions states that internal web servers work but external ones do not. If wireless were the issue nothing would work at all. The issue is more likely to be related to external DNS, a firewall or an issue with the proxy used to connect outside the local network.
