A virus has infected the system
Corrupted BOOT.INI file
Boot sector corruption
Copy the missing file from another computer and reboot.
Execute a Windows repair from the Windows setup media.
Boot into the Recovery Console and execute FIXBOOT.
Reboot and press the F2 key when prompted.
Loop back plugs
Use recovery console and the FIXMBR command.
Use recovery console and the BOOTCFG /REBUILD command.
Use recover console and the FIXBOOT command.
Use recovery console and the CHKDSK command.
The subnet mask is not correctly configured.
The DNS client has not been configured on the computer.
The DHCP client is unable to obtain an IP address from the DHCP server.
The default gateway is not specified.
A dead CMOS battery
The OS is not installed on the hard drive
A faulty RAM
A faulty HDD connection
They are using the wrong WEP key.
They have been infected with malware.
They have lost Internet connectivity.
They need to update their network device drivers.
Netsh firewall show logging
Netsh firewall show state
Establish rules in the email scheduling program to perform updates.
Select "Update Now" from the program options.
Use "Windows Update".