How do you clear the computer memory that pops up previous searches or sites that were entered?

When I type a single letter into a google or yahoo search, previous sites and words pop up in the drop down and I would prefer that they not appear. How do we clear this. I have tried the clear search setting, but that didn't have any effect.How do you clear the computer memory that pops up previous searches or sites that were entered?
Ctrl - Shift - Del in Firefox. I do not know what it is for IE.How do you clear the computer memory that pops up previous searches or sites that were entered?
on ie go to tools then general then the delete button click it


but im using vista it might be diffrent on xp or 98 but i odnt think so (sorry dont)