Windows 7 64-bit laptop has developed a nasty habiot of not running any MS apps. Instead flashes up error box that says 'Error 1719 The Windows installer service could not be accessed. This can occur if windows installer isn't correctly installed'.
Have unregistered/deregistered (?) msiexec and registered it again and tried the register change shown at http://support.microsoft.com/kb/2642495
Firefox works but little else.
Is there a complete fix?
Worth doing a system restore?
Or do I have to reinstall Windows etc.?