? 
The search history that displays in the search box on the Google homepage is stored by your browser, not by Google. To disable this feature in Microsoft Internet Explorer (IE) versions 5.0 and higher:
- Choose Tools > Internet Options.
- Select the Content tab.
- In the Personal Information section, select AutoComplete.
- Click Clear Forms.
- Click OK.
To keep this information from being stored in the future, you can uncheck the "Forms" box in the Internet Options window. Alternatively, you can delete individual entries from your search history by using the Down arrow key to select a previous search, then pressing the Delete key once an unwanted search is highlighted.
If you have Toolbar 4 or 5 installed, you can clear your Toolbar's search history by clicking the drop-down arrow on the search box (not the arrow beside the "G"). From the drop-down menu, select the Clear History link.
Please note that this only clears the search history from the Google Toolbar, which is entirely separate from the search history stored by your browser.
For Toolbar 5:
- Click the wrench icon on the Toolbar. The Options window appears.
- Select the Search tab.
- Uncheck the box next to Store search history on my computer.
- Click Save.
For Toolbar 4:
- Select Settings > Options on your Toolbar to open the Options window.
- Select the Features tab.
- Click the Search Box Settings button.
- Uncheck the box next to Suggest from my search history.
- Click OK.