Webby - 2006-02-26

This is the error that I get:
[URL=http://img109.imageshack.us/my.php?image=image12ak.png][IMG]http://img109.imageshack.us/img109/7105/image12ak.th.png[/IMG][/URL]

It says "This software cannot be installed on this computer". But I don't understand why it can't be. I have a legal working copy of mac os x 10.4.3 from my mac mini. But I get this error. :( Please help.