Windows has a built-in feature that lets you flexibly remap keys by adding registry keys corresponding one keycode to another.
This isn't very user-friendly to do manually, so you can get a program called SharpKeys that's a nice GUI to this.
- Just install the program (it's small); start it up.
- Press Add below the empty list box.
- You can then choose Caps Lock from the left list and Left Control or Right Control from the right list, or do it the easy way and just click "Type Key" on the left and press your caps lock key and then okay.
- Then do the same thing on the right with either Left Control or Right Control.
- Then just hit OK, then hit Write to Registry in the main window.
- Once this is done you'll need to log off and then back on so that Windows will reload the keyboard settings.