Windows Vista: start menu icon changes on its own: worrying?

Alright, when opening the start menu on Vista 64bit, there’s a small picture in the top-right quadrant (the administrator icon), which you set manually upon first starting the computer, and subsequently at any point by clicking on it and opening the User Accounts window.

Now, a little while ago I noticed that the photo I had set as the icon disappeared, and was replaced by a circle with the four windows colors and a bright green check mark. This icon stayed for a while, then disappeared back in favor of the icon I had actually, manually set.

So has anyone seen this before, or have any idea what it might be? I have an antivirus and anti-spyware program running, but I’m still worried about a virus, hacking, or some other kind of incursion or risk that my lack of much tech-savvy makes me paranoid about.

It changes by itself if you hover over items on the RHS of the Start Menu. Different entries have different pictures. The icon you saw means your mouse pointer was hovering over ‘Default Programs’.

…huh, now that’s just downright weird- I never noticed that before.

Thanks for the reply!