well i have a shop and how can i make signatures using these from my computer:
Microsoft office word 2007 or Microsoft office powerpoint 2007 and can you make avatars to?

you can't.
microsoft word is to write documents and microsoft powerpoint is to make power-point presentations, which are slideshows, and things.
they're mostly for office or student use, not to make graphics.
i recommend trying some graphic-making sites, like lunapic.com or photobucket.