Question: How do I crop videos with Virtualdub?  
 
Answer: People are often searching the cropping option under the filters but it's not quite here. In fact, you can apply cropping to just any filter. To do this, click on Video > Filters on the menu then add a filter. Once it's done, select this filter on the list and click on the 'Cropping...' button on the bottom-right of the window.  
 
If you don't want to apply any special filter, you can use the 'null transform' filter (which doesn't do anything) and then use the cropping options. If you have many filters, I recommend you put the cropping option in the first position, that way you'll save some precious CPU time.