In preparing to update a computer from XP SP3 to Windows 7, somehow Explorer.exe was corrupted/lost.  The computer boots to a fancy, blank screen.  The error message is:
Explorer.exe - Unable to locate component
The application has failed to start because Normaliz.dll was not found. Re-installing the application may fix this problem.
So ... I've been searching for a download of Explorer.exe for Windows XP SP3 and entered a labyrinth of "fixes", including this one: 
http://en.kioskea.net/forum/affich-526383-explorer-exe-doesn-t-startNo luck.
I can get to Task Manager, New Task, and Browse.  I've connected an external hard drive that, if it had the correct version of Explorer.exe, perhaps I could run Explorer.exe from there??
Or edit the Registry?  Explore.exe is in several places in the Registry.  Except not where Windows needs it at Startup?