Actually I have to agree Mara :
If your version of Windows isn't activated, then its either locked up because it wasn't activated, or you haven't used up the 30 days you are allowed in which to activate it. If thats the case, Windows will be annoying you regularly with those stupid popups nagging you to activate it, and you will have an icon on the taskbar for the purpose of activation lol
In the case of Vista though, which I had installed recently but didnt like much, if you check out the systems properties page, at least it will tell you how many days you have left. I didnt see an activation icon on the taskbar in Vista, (though this may not normally be the case, as my Vista was ummm a little different - cracked

) but I was able to watch how many days I had left in the systems properties.
This wasnt actually an issue for me anyway, as the effect of the crack was to reset those days whenever they got close to zero!
My assumption, and those who have genuine copies of Vista will be able to confirm or deny this, is that in Vista there is no activation icon and you would need to check out system properties to see how much time you have left. In XP, the icon on the taskbar and the nag messages will tell you this.