Hi Sylvia,
if I remember correctly, it came with version 22 installed. When I noticed my USB drive wasn't recognised in both the bios and boot menu I upgraded to the latest version (24).
When that didn't work either, I read somewhere on this board an older version would work, and it did. That's when I downgraded to version 21.
Because I experience troubles with surround sound over HDMI also (handled in another thread) I again upgraded to the latest version. I hope I won't have to use my USB stick to boot from in the near future....