Would it be ok to revert back to the previous version of my BIOS? I've heard that's risky, as it's flashed onto the chip, and can damage it.
no more so than the risk you take whenever you flash the bios. But I would not revert, do what I said above, check your bios settings that they match what you had before, especially boot sequences for floppy, hd, cdrom. Check, memory, pci bus, etc. Make sure the settings match your hardware, you may need to go into the pci settings options and set 'reset configuration data' or similar title to 'enabled' then reboot. This often needs to be done when you add new hardware and your pc won't boot but may apply here since the bios flash put settings back to default which may cause a hardware conflict.
Try playing with the bios settings for awhile before risking trashing your bios chip with a possible bad flash.
Looks like you reformated the HD and reinstalled Windows. Now LILO's gone. Normally LILO is used on a blank hard drive to create partiitons, then Windows is installed on the one you created for that. Else windows ends up in charge and always screws things up. I think you lost the geometry and a lower one came back. Is the HD a smaller size now?
Leave the BIOS, or upgrade it further.