Well, that is a pet peeve of mine, Trusted Installer is not as much a security concept as a limiting of freedom
In the good ol'times of NT and 2000 "pro's" (which implied network, shared pc's etc, AND often an IT supervision) had a all in all "sound" security/access implementation, and the "normal users" (your home PC and laptop, probably never connected to a network) had a simplified model with 9x/Me,
With XP, it was forced down the throat of common users a whole load of access/permisisions and what not that simply made no sense.
With the (stupid) Vista and later there were not that many (or good) improvements (in the sense of actual increase in security in practice), as each and every (stupid) additional roadblock has been - before or later - worked around, the only effects were to make the life of users (and in some cases of developers a little more miserable).
And if you would tell us which among the various proposed solutions/workarounds you used successffully that would maybe be useful to someone else with the same or similar issue.
jaclaz