Windows 7 UAC lightbox is slow to appear - can it be sped up?
Solution 1:
Is this when you deal with larger installer files? UAC scans the files for security directives embedded inside, for larger files this will take longer.
If the darkening of the desktop is bugging you, you can turn UAC down 1 level from the default, which turns off the "Secure Desktop" feature. Your desktop won't dim but UAC will still prompt you as before. The UAC prompting will feel snappier too. The dimming may be a little slow on the integrated graphics, making the whole UAC process feel slow.