To access the downloads for your Vaio, you need to find the correct model name it will be something like VGN-NW21MF.
You are quoting the name of a group of Vaio models with the same casing but for downloads you need the unique model.
When you have the model there will be a Support Webpage for it including all available downloads. Here is the Support Page for the VGN-NW21MF - but there does not appear to be a BIOS Update.
https://www.sony.co.uk/electronics/support/downloads/results?query=VGN-NW21MF
