Microsoft Office for Mac Icons

My questions deals with the icons for Office programs. I am running Leopard and in some places I can see the Office icons associated with the file, like in a folder on my desktop. But in my documents folder and other folders on my desktop there are word and excel files that don't reflect the Office icons. Just a black/white generic XLS or DOC name on the file. It's just not consistent. Any ideas how to correct this problem?

Thank you.