Need Explorer.exe

Hello,
Does anyone know where I can download explorer.exe? Here's the scenario:


I recently ran Avast 4 Pro to scan my computer (start up boot scan). When my computer restarted, my icons and task bar will not load. I looked in my task manager and explorer.exe is not running. When I try to run explorer.ese via New Task, it tells me that "application cannot be run in Win32 mode.". I then tried to open Avast 4 via C:\Program Files\Alwil Software\Avast4, it gives me the same error message.

Computer Specs:

Toshiba Satellite M115-S3094
intel Centrino Duo
Windows XP Media Center Edition