In order to clear the search history in AVG Toolbar for Mozilla Firefox:

1. Open Firefox
2. Type about:config at the address bar and hit enter.
3. Type avg.toolbar.searchHistory at the filter and hit enter.
4. Double click the avg.toolbar.searchHistory line.
5. Delete the contents of the opened box and click OK.

In order to clear the search history in AVG Toolbar for Internet Explorer:
1. Close Internet Explorer
2. Go to Control Panel > Folder Options > go to View tab > select Show hidden files and folders. Click OK.
3. In Windows XP, you’ll need to delete the file COMBOSEARCH.acs. The file is located in C:\Documents and Settings\\Application data\AVGTOOLBAR\COMBOSEARCH.acs
For Windows Vista, the COMBOSEARCH.acs file will be located in C:\Users\\AppData\Local\AVGTOOLBAR\COMBOSEARCH.acs