I can't figure this out so I hope someone can help me out. On my MBP, I get prompted for a PW before any program gets installed. On my iMac, at times I get prompted, other times I don't. I just downloaded handbrake and installed but there was no PW prompt. The day before I installed a plug in for Quicktime and was prompted for a PW. How can I get so that I get prompted for a PW every time before anything gets installed?