The latest BIOS for the Sony VAIO VGN-FZ series is R1120J7 which can be downloaded here
https://elektrotanya.com/sony_vaio_vgn-fz21z_pcg-391m_r1120j7_bios.rar/download.html
you can flash this with Winphlash which can be found on wim's bios website at
https://www.wimsbios.com/phoenixflasher.jsp#gsc.tab=0 (scroll down and find Winphlash)
Here is video show you how to do it: