1. If all on a single GenoMap, open Table Layout, Individuals and and click on 'Age' column label to sort into descending order of age. Click on 1st individual and drag down to select all aged 100 and above. Click on the GenoMap, where these individuals should have selected. Press the X key and you're done.
2. If spread over multiple GenoMaps using the Report Generator Skin Template {EN} XML Toolkit. Select the Miscellaneous Edits tab and check the box to delete tose ove a certain age, specified in the box below it.