As above: you will need some hardware to input the video onto your machine, unless you already have it built into your PC (not common). 9 times out of 10 the hardware comes with basic software to both capture and edit the video.
As people have said, it is a "real time" operation - a 2hr film will take 2 hours to copy. You will probably also need to add processing/conversion and editing time.
As has been stated, copy protection may be present as well. On the whole it is a lot less hassle to search for a cheap DVD copy. However, if the films are home videos or unobtainable otherwise the method I use is this:
VHS copied direct to DVD-RW in a DVD recorder.
Take DVD to PC and copy video files to Hard Disk.
Use VideoReDo TV Suite to edit and reassemble video.
The output can then be saved/converted/used to create a DVD.
I used to use Mpg2Cut2 for the editing (which is free), but it doesn't seem to work well with Vista.