I have ATT.net, on my desktop, the mouse would not work, so I checked connections, everything is connect correctly. It would not do anything , so I turned everything off and waited 15 mins then turned everything back on. Ssid for me to reboot. My Son-in-Law Tom who is now in Baton Rouge, built my computer but I have no reboot disk. My desktop is asking me to reboot first device: question is which one do I choose to reboot from? the hard drive, or Legacy Lan or USD - FDD, USD-ZIP(don't have) USD-CD Rom, or USD-HDD.
You always boot from the hard drive... unless it won't boot. If there is an issue with the hard drive or if there are some corrupt boot files, then it won't boot. Also, if you have a floppy drive, make sure there is no disk in it.