All that is correct, but it needs (a) support in software and (b) the outside party having secret values mathematically related to the "attestation key" embedded in the TPM. The OS designed for this kind of system then uses the TPM to verify the signature, hash or whatever of software, and would either shut down any unapproved software or deny access to the DRM'd data.

I don't know whether Windows 8 is like that, but anyway you can opt out of it by using an OS that doesn't support any remote control. In many BIOS's you can turn TC support off.

Here is the formerly canonical, maybe dated now, overview of TC http://www.cl.cam.ac.uk/~rja14/tcpa-faq.html