Link: http://vcl.vaio.sony.co.jp/download/SP-014674-07.html
Scroll down and click on the last available green coloured button.
The BIOS Update is also for TZ90S with English OS.
It is already the second BIOS update available from Sony Japan for the TZ90S.
Also available are driver updates, most important are the camera module and camera utility updates. They work with the English OS too.
Caution: some of the other updates are in Japanese.
Link here (scroll down to the second part of the page!!!):
Also a hint regarding the latest INTEL graphics card V 15.4.3 driver (updated from their website, Intel pulled it off a week or so later):
a lot of owners complaint about severe display flickering under certain conditions. This doesn't mean that your TZ90 is faulty, there is a registry setting which has to be removed, the Intel driver is to be blamed for his problem, not the hardware.
If you experience this problem, please post it and I'll explain how to fix it. It involves using regedit and deleting an entry from the registry, so this is something which shouldn't be done by a beginner.
DO NOT send your TZ90S in for a repair, there is nothing wrong with it, the display flickering is caused by a faulty entry in the registry caused by the latest Intel graphics card driver from their website (which has been already pulled off from Intel's website for obvious reasons!).