As the Support website has just been upgraded, I'm not sure if this is possible online.

In the UK, the standard warranty starts on the date of purchase (to be supported by proof of purchase) and ends 12 months later. However, if your SB is one of the models with Windows 7 Professional (or Ultimate) preinstalled at the factory, the warranty ends 24 months later.

If in doubt, please check with Vaio Support who will check the Registration Date for you. (Tel: 0870 2402408)