MSI has added a series of updates to the newest versions of BIOSes for B75A-G41, B75IA-E33, Z77A-G45 Thunderbolt, Z77A-G45 and Z77MA-G45 boards.
It appears that the focus was on improving PCI-E display card compatibility but also memory compatibility, the latter being noticeable in every version, from the first to the last BIOS.
Z77A-G45 Thunderbolt, Z77A-G45 and Z77MA-G45 boards get a CPU micro code update. B75A-G41, B75IA-E33, Z77A-G45 Thunderbolt and Z77A-G45 boards now benefit from a Realtek LAN update, while the Z77A-G45 board, along with its 2.8 BIOS, features improved gaming keyboard compatibilities.
All of the boards mentioned above support Microsoft's latest operating system.
Bear in mind that, if you want to update your BIOS, you should use a bootable USB flash drive instead of the MSI LiveUpdate Tool, or do so directly from a floppy disk – at least according to the recommendations of forum users.
This said, if you decide to flash your BIOS, follow the links below and download the appropriate version compatible with your board:
Intel B75 Series
Intel Z77 Series