I seem to remember the Yahoo! Search Bar at least being in the Add/Remove Programs list, so you could uninstall it like any other program. Probably the Google one, too.
1. Go to view
2. Click on Toolbars and click on the ones you wish to remove. They might appear under another' search engine's name. For example my yahoo toolbar shows up as MSN.
EDIT: Or did you mean delete it? What was said above should do the trick.