Are you talking about the Google toolbar or the Google website, Walworth? If it's the website, in IE go to Tools > Internet Options > Content tab, click the Autocomplete button then the Clear Forms button.
Why have you got two posts for the same question. The answer I have given in the other thread is
"If you are using the google toolbar, click on the word "Google" (left hand edge of toolbar), click on options and untick "Drop-down search history". If you then click on Apply your problem will be solved."
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