"Microsoft and several PC vendors have teamed up to ensure that only operating systems bearing Microsoft’s cryptographic signature will be able to boot on their hardware, meaning that unless Microsoft has blessed your favorite flavor of GNU/Linux or BSD, you won’t be able to just install it on your machine, or boot to it from a USB stick or CD to try it out."

— Lockdown: free/open OS maker pays Microsoft ransom for the right to boot on users’ computers - Boing Boing