This page is a little Windows utility that lets you swap the Alt and Ctrl keys, or make the Caps Lock into a Ctrl key, for Microsoft Windows.
Download it for $3. Use the paypal button below. In the comment field, put “swap Alt and Ctrl”. I'll email you the download link. Make sure your email address is included and correct.
Or, to do it yourself, you'll need to download AutoHotkey, and load this script.
; -*- coding: utf-8 -*- Ctrl::Alt Alt::Ctrl
See: AutoHotkey Tutorial
For general tools, see: Keyboard Layout ＆ Key Macro tools for Windows.