A user reboots a machine.

When a user hears one beep on rebooting a machine, and then an error message is displayed, it could indicate that there is a problem with the RAM module or the boot order. The beep sound indicates that the POST process was successful, and the error message indicates that the boot process was unsuccessful. The boot order determines the sequence in which the computer looks for bootable devices. References: CompTIA A+ Certification All-in-One Exam Guide, Tenth Edition by Mike Meyers (Page 693)