The simplest way to temporarily disable your touchpad is FN F5.
Previously, I installed ELAN Touchpad driver which allowed me to use the touchpad to move the mouse but not double-click. This was fantastic until I forgot to bring a mouse with me one day and was unable to use the PC properly.
When I finally got my mouse, I went to reenable the feature but kept getting “Windows Shell DLL Error”.
After some searching, I found a thread that recommended uninstalling the Elan Touchpad App using the “Add Removed Programs” function and it worked.