Changing W2K product key

I work for a small company and we’re currently in the process of making sure all of our Windows 2000 licensing are legit. We found a couple of PCs sharing same license keys. Anyhow, what we’d like to do is change the W2K license key without having to reinstall the OS. Is there a simple and effective application that can do this?

I’ve looked around on other forums and found some freeware application but they only work on Windows XP systems (RockXP, XXPID, KeyFinder). Please help. Thanks.