Hey and welcome to the AVForums,
Ok ... your description is a little vague but, I guess you want to feed your xbox video out into the back of your computers S-Video IN?
If this is the case, im fairly sure you can do this but the only way I could do it, off the top of my head, is not pretty
Go back to the original xbox scart cable you got with the Xbox - this is a scart socket on the "output" side not the rca(?). Now get one of the crappy little scart switchers from Argos and whilst you are there, pick up a scart to S-Video adapter. Now plug these together with a normal s-video cable into the back of your computer video IN socket .... hey presto
Picture quality is not all that as its a mess of connections and there probably is another way of doing it, I just don't know it

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