Dumb install question

Hi, I installed home free version on my kids’ computer. I’m the administrator and the software loaded fine under my user name, got the key, all is well BUT can’t seem to activate the software on the four other user names. On their desktops, the icon appears on the desktop but not in the task bar (lower right corner). When I plugged in the installed key, I got an invalid key message. I changed all of the kids’ accounts to administrator (scary) and tried again but still no go. What do I need to do to have this operative for all users on one machine (XP). Thanks!

You don’t need to activate the software in common users accounts.
Are they ‘kids’ logged as an administrator? Don’t do it…

Are your system time and date correct?
Go to the SSL page version and register from there: https://secure.avast.com/scripts/register.php?lang=ENG

See the tutorial: http://www.avast.com/files/tutorials/insert_key.htm
Please take a look here: http://www.avast.com/eng/faq-invalid-license-number.html