Most eMachines computers have a Recovery Partition which can be used to format the machine and reinstall the operating system and all drivers and software back to its factory state. Check the eMachines site for the instructions for such or depending on the make an model of your eMachines, the Recovery partition steps may be a little different.. Usually, the best method is to restart the computer and press the appropriate F-key to access the Recovery partition.. Or, sometimes, there is a "System Recovery" icon in the Start Menu.

Hope this helps.