Most computer manufacturers will inform you in one way or another that unless there is a problem that will be solved by updating the BIOS, you should not update the BIOS. Roughly translated... If it ain't broke, don't fix it.
BIOS updates rarely (if ever) add functionality that was lacked. BIOS updates add newer processor support (seen more in desktops than laptops) and fix issues that were created or exposed in previous BIOS revisions.
Most importantly, most laptop manufacturers stop creating BIOS updates after a year or two of the release of that model laptop. Why? They've worked out the existing bugs in that model, they have moved on to newer designs, they don't intend to add newer processor support (to make you buy a newer laptop rather than upgrading your existing one), etc. Rather than spend time creating BIOS updates for models they no longer make or sell, they spend their time making BIOS updates for their current models.
Sony USA doesn't recognize that model... but Sony Germany does They do not list ANY Bios updates available for that model... which means they might not offer any.
So again... why do you want/need to update your BIOS? Presenting the problem that requires a BIOS update might get you better results... because if you want to update your BIOS because it seems really old... that's not a very good reason.
EDIT Apparently VT was disabled by Sony on purpose, but later decided to be added back in through a BIOS update, for some of the VAIO series lines. The following laptop series had BIOS updates released: Sony decided to enable VT for the following model series lines: VGN-AW Series VGN-CS Series VGN-FW Series VGN-NS Series VGN-NW Series VGN-P Series VGN-SR Series VGN-TT Series VGN-Z Series. Unfortunately, yours is not included in a series that had a BIOS update that enabled VT.