You're not the first to ask.... I suppose that it's Sony Vegas ur using, if it's not then
this guide won't help u. Anyways if ur using sony vegas u can see with that guide how to speed up a clip.
To shorten a clip down is really really simple. U can either to the way I describe to cut clips, a bit harder method. Or u can do it the easy way.
1. Click on one side of the section of the movie you want to make shorter.
2. See to it that u got the square one and not the semicircle one.
3. Drag it to the where u want the clip to end. If you got snapping enabled, u usually do, u will automatically get "stuck" when u come to where the first clip ends. You will see what I mean when U try it.
It may seem hard when u read, but try a little for urselves and u will reallise it's pretty easy. Hope it helps.