I have an HP ProBook 4520s that the touchpad is not working on. Interestingly enough, no external mouse will work either. I cannot say exactly when the problem started happening since it is not my personal laptop, but here is what I have noted/tried.
PC is Windows 7, 32-bit, SP1.
1) Touchpad has a light in the corner that is not on at all. Tapping it has no effect.
2) Device Manager -> Touchpad and External Mice both load with Code 39 (Drive corrupt or not found).
3) Tried a system restore back 3+ months when I know it was working, did not fix.
4) Touchpad/Mouse does not work in Safe Mode
5) Touchpad/Mouse does not work with a Clean Boot or Diagnostic Boot.
6) Downloaded newest drivers for touchpad from HP and installed.
7) Removed current drivers for touchpad (uninstalled in devmgr) and deleted from PC. Redownloaded and reinstalled.
8) Noted the external mouse and touchpad only had 2 drivers in common, sys32/mouclass and sys32/mouhid . Deleted both files and replaced with known working files from a working machine of the same OS.
Any help is greatly appreciated.