Issue with vista and windows 7

[Alkorin]

The dim isn't useful in and of itself. The secure screen is useful because it doesn't allow malicious programs to tamper with UAC.

If you're going to turn off that screen, you might as well turn off UAC, to be honest. If you know what you're doing (read: you don't click Yes on every window that pops up) and you have an up-to-date virus and malware scanner, you're probably fine to turn it off anyway.