If you have an external hard drive that is always plugged into your computer, you can enable write caching to speed up performance significantly when writing to the disk. Write caching isn't enabled by default for external drives because removable devices could lose data if you unplug them too quickly, so take care when using this setting.
To change this setting, simply type 'Device Manager' into the Start menu search box and press enter. Browse down to the external hard drive that you wish to enable write caching on and double-click on it to open up the Properties screen. Change the setting to 'Optimize for performance' and click 'OK' to continue. Reboot your computer for the settings to take effect.