Blue Vertical Line on the display.

The problem appears because you do not have proper drivers either for your graphics card or monitor.If the windows does not find the right drivers, it installs the default drivers.Thus, you may not be able to push further than a particular refresh rate.Install the right driver for your monitor and increase the refresh rate.

hii varathri.

plz check ur RAM memory.
remove it .clean it . and insert it proprly.

also reinstall the display driver from drivers cd u might have recieved with the pc.

also if u r using graphic card .reseat it and also reinstall the driver fro the same.