You are correct to assume that it has been disabled in Vista to prevent the possibility that people may use it to illegally record sound. It is not just Sony that have had to do it, but all manufacturers.
We are sorry that it affects users who are trying to use it for honest purposes like yourself, but we are bounded by law the same as other makes.
I can not predict that there will ever be a change in the policy. We are aware tough that there are 3rd party software/methods of getting around this issue, however we cannot advise or recommending using them.
Should you have any further queries, please do not hesitate to update your case. If you would prefer an e-Support agent to contact you by telephone, please update your case with your preferred contact number & a suitable time frame between the hours of 8:00 to 18:00 Monday to Friday.
Sony Vaio-Link Team