Copy-Protection, License-Enforcement, DRM and VISTA

I am a developer in a small company that develops DRM, copy-protection and
license enforcement tools for Windows developers. Our tools currently allow
the client to create licenses and integrate our run-time components into
their software to enforce a variety of license models.
Many of the mechanisms that provide this functionality, such as hiding
redundant copies of the license in hidden and inconspicuous locations on the
system and the registry are simply not going to work on Vista. Many
operations the run-time performs to detect hackers will require permissions
not likely to be present by default and naturally a hacker will refuse to
allow.

We are willing to redesign and adapt (we must - or we will die).

My question is - what does MS want Application DRM providers to do? What
avenues has Windows left open for us to provide functionality that:

a.. Detects if the user has installed a copy of a given application
before? (This would require that uninstalls of the product always leave
something behind the user can not easily see or find).
b.. Detect if the user has tampered with certain files (This would require
that hidden or secure copies of the files can be compared against on the
users system).
I guess this boils down to: Is there a secure, hidden location we can store
information on the users system that will not get removed on an uninstall
that we can reliably read, write, create and delete - without alerting the
user? I suspect the answer is "nowhere". If so - what do the hundreds of
thousands of software developers do that need to protect their application
from illegal copying? How do we create trial versions that aren't easily
defeated? etc.

Thanks for your feedback.