i had the same problem. arcgis 10 has changed from arcgis 9. apparently all the functions of the drop down menu are available somewhere in the "geoprocessing" menu drop down.
I'm trying to do a college project that is due in in early jan, and my university which was supposed to be open until then has closed down due to bad weather. I have a set of instructions based on an earlier version which is useless to me!!