It will be irritating to anyone if a program changes default search provider for a browser. The program may install as an add-on or as a toolbar and changes default search provider without users permission. However this can be preventable in IE8.

Sometimes some toolbars will be installed along with freeware programs or others, without users consent and are difficult to uninstall also. If a toolbar or add-on tries to change default search provider in IE8, IE8 shows a dialog box whether to keep or change your current default search provider, then check Prevent programs from suggesting changes to my default search provider .

Another you can do that is

1.Open Internet Explorer, select Tools>Manage Add-ons click search providers  and check “ prevent programs from suggesting changes to  my default search provider” and click close.

prevent changes to default search provider in IE8

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