suspicious "click to run" for windows pops up

a window randomly pops up saying click to run, and the message says that an update for windows starter is available. do you want to download it. i always close it clicking on the X but others on the computer have pressed cancel, as far as i know. I know it is not a real windows update but my windows security essential doesnt pick it up.
if anyone can help me i would very much appreciate it!
thank you