If you want to have your CA certificate added to the trusted root stores of
the computers in your organization, Active Directory can do this for you
automatically -- indeed, if you have an enterprise root CA, the CA
certificate is already present in the stores of computers that are domain
joined. You could also use the Internet Explorer Administration Kit to
create customized builds of IE that contain only the trusted roots you want,
including your own.
If instead you're looking for a way to have your CA certificate added to the
list of trusted roots that are included with every installation of the
operating system worldwide, that is an endeavor that takes quite a long
time, involves some rather thorough investigation of your organization,
requires that you are running a public CA, and costs several hundred
thousand to several million dollars.
