Internet Explorer 8, on Windows 7, should have a search box at the top right of the screen (with a magnifying glass symbol in it). If there's the Google symbol (a white 'g' on a blue background) there, the box will automatically use Google as the its search engine. If not, try clicking on the little black arrowhead, pointing downwards. That will enable you to select from the other pre-loaded search engines. If Google isn't among them, see here:
http://windows.microsoft.com/en-gb/windows-vista/change-or-choose-a-search-provider-in-internet-explorer