Sure, here's how you can delete cells with values less than 100 in a large range of cells in Microsoft Excel:

1. Select the range of cells that you want to delete values from.
2. Click on the "Home" tab in the ribbon at the top of the screen.
3. Click on the "Find & Select" button in the "Editing" section of the ribbon.
4. Select "Go To Special" from the drop-down menu.
5. In the "Go To Special" dialog box, select "Constants" and then check the box next to "Numbers".
6. In the "Data" section, select "Less than" and enter "100" in the box next to it.
7. Click "OK" to close the dialog box. This will select all cells in the range that have a value less than 100.
8. Right-click on any of the selected cells and choose "Delete" from the context menu.
9. In the "Delete" dialog box, select "Entire row" or "Entire column" depending on whether you want to delete rows or columns with values less than 100.
10. Click "OK" to delete the selected rows or columns.

That's it! This should delete all cells with values less than 100 in the selected range. Just be sure to double-check your data before deleting anything to make sure you're not accidentally deleting important information.