Lots of people are having problems using Ulead Video Studio with Easycap on both Windows XP and vista. I was trying to use UVS 10 (which came bundled with my Easycap) and could not capture at all with it on Win XP SP3. Video capture and editing can be quite daunting when you first get into it, I'm still relatively new to it all myself!
There is some free software called SUPER that will let you rip the sound from any video file, you could then mute the sound from movie A, rip the sound from movie B and then import it into the project! If you continue to have problems with Ulead Video Studio don't give up with EasyCap, there is lots of free video capture/editing software out there that might work with it on your system. Click
here to see some.
What exactly are you wanting to capture? What do you want to do with it after? If you tell me precisley what you want to do I will try my best to assist you if I can.