If I have a....

[SteveDVD]

...capture card in my PC and if I started playing a DVD on the TV and started the capture card to capture the TV would it capture the DVD?

[Vejita-sama]

Should work. I assume your TV as a video out? And (not to be rude) but you've got the setup, so give a try and see what happens

Let me add that a rip from a DVD-ROM will ALWAYS produce better quaility then a capture. Plus it's a lot faster. Not sure what you're trying to do thou.