In the absense of a utility from the makers of Quickheal to remove their program cleanly from the PC I would download and install Spybot Search and Destroy from http://www.safer-networking.org
When that is done and you've updated the program (which will cause it to restart), click on "Mode" from the menu bar and choose "Advanced." Acknowledge the warning screen and proceed to the "Tools" page by clicking on the button for it.
When the tools page is open, click on the "System Startup" option. When that is open, find and uncheck all startup items relating to Quickheal.
Reboot the PC, Quickheal will not be loaded because you removed it from the startup group.
Your PC should now be running the Avast A/V by itself and it's operation should be returned to normal speeds.