To cut time from an movie in VirtualDUB first you need to load it into the program using File / Open video file.

Next, from Video / Select Range…

You can specify the start, end and length of the part which you want to cut.

Other way to specify the start and end of this part is to move the slider in time scale at bottom to start position and click on Mark In control like shown on the picture.

For specifying the end point move the slider in time scale to end position and click on Mark Out control like shown on the picture.

Now you have the selected part which you want to cut colored in light blue on timeline.

When you specify part for cutting go to File / Save As AVI…, select folder and name for new file and press Save.

Next, depending on your movie size, time, applied filters and performance of your PC you have to wait while your new movie will be saved.