So you want to make your Caps Lock key a Control Key under Windows. This is what I've had to do since Windows NT, but it works under Windows XP up through Windows 7. Caveat: I'm not responsible if you destroy your registry. Procede with all due caution.
You'll need to edit your registry. shudder. Still, if you don't corrupt the registry and have to reinstall your box, it is great to have your Caps Lock work as a control key. You have a couple choices, really: (1) swap CapsLock and Left Control, or (2) make CapsLock and Left Control both be Control Keys... who uses CapsLock anyway? The solution path is essentially same for both:
Run 'regedit' (as Administrator), and add the following key in your registry:
Note: you don't want Keyboard Layouts! No plural here! When Keyboard Map is highlighted, select Edit -> New -> Binary Value. The name of the new value is "Scancode Map". Once it is listed, double click it and you will get to enter in the value code.
SWAP CapsLock and Left Control:
Make both CapsLock and Left Control be Control (so some people won't find your workstation unusable when they try to use the Left Control key...):
It should look like this: