In Windows, the Explorer windows (aka shell windows), the navigation bar (back, forward, address / breadcrumb bar / search) is fixed at the top. IE will do the same, for consistency with the shell
as well as anti-spoofing.
Doesn't toolbar customization make it harder to spoof the chrome?
I know when I'm surfing on a Mac, and a spoofed Windows dialog pops up, I get a good laugh.
LUA won't stop users from infecting themselves with spyware. But it will make sure they don't infect other users. So Mom will get much less spyware by giving Junior a limited-user account. (And vice versa.)