I have a vgn-fw21m vaio. I updated it with the latest bios found on the sony support page. I bought a new compatible battery that has to update the bios to an earlier version. I cannot do it. It gives me an error like: "IHSI: get support mode fail in SMI! "
Can anyone please help!!!
If what you mean by compatible is that the battery is not manufactured by Sony then you may have big problems. If the battery was made for the earlier BIOS version of the Sony in question it would seem likely that Sony has changed the BIOS so that it is no longer supporting that battery brand. This may have been deliberate or it could be a side effect a BIOS upgrade that was required for different reasons.
It is possible but that is something you should check into before you do it. Flashing the BIOS can have unintended consequence as you have recently discovered. Here is a link that demonstrates people having battery BIOS issues. One guy has even turned his laptop into a brick. Imo you should return your battery and obtain a Sony battery. If these guys experiences are anything to go by you have gotten off lightly so far.