how can I download yahoo toolbar onto my new computer that has google toolbar? How can I changed toolbars?

if you want to get rid of google toolbar go into programs, add remove programs, you will be able to see the google toolbar program there, highlight it and click on uninstall. then you can download and use yahoo toolbar as you wish.

Try what this article says:
Make sure you only download the toolbar from toolbar.yahoo.com or downloads.yahoo.com

Make sure you hit the yellow bar to allow active x when down loading. Hit view above and enter toolbars to see if you have. Click it for a check mark to show it.