update the firmware of your router
unplug and replug it from the wall
try a different lan port
which lan driver version is currently installed on your PC?
any third party antivirus and/or firewall installed?
ethernet connection is set to private and not public in windows?
reset any overclocking to default values
uinstall cfos if installed installed
to have a look what the problem could be:
run userbenchmark.com and post the http link of your result, e.g.
https://www.userbenchmark.com/UserRun/28977730
Reset the BIOS by jumper clrCMOS or JBAT or similar (eventually you will have to set the boot priority correctly after that)
check windows integrity
open the command prompt as administrator and type DISM /Online /Cleanup-Image /RestoreHealth
https://www.lifewire.com/how-to-open-an-elevated-command-prompt-2618088
https://answers.microsoft.com/en-us...em-files/bc609315-da1f-4775-812c-695b60477a93
clean boot
Describes how to use the clean boot process to troubleshoot a problem in Windows 8.1, Windows 8, Windows 7, or Windows Vista.
support.microsoft.com
check the memory by running memtest.org usb autoinstaller (bootable USB flash drive)
check the hard drive for errors with its manufacturer´s tool