when its running on mains it should show a small green light on the front of the laptop along side the battery light, etc have tried contacting sony?
http://www.vaio-link.com/index/index.asp?l=en
ive got a vaio 217m laptop the keyboard died a few months ago emailed there support team and they took me through a few tests and i sorted the problem, they also do reapirs for a small charge

hope this helps