How to check the BIOS version ?

To check the BIOS version, you can run the dmidecode command.
Unfortunately, you can't easily grep for the information, so piping it
is a less efficient way to do this. On my Lenovo T61 laptop, the
output looks like this:

#dmidecode | less
...
BIOS Information
Vendor: LENOVO
Version: 7LET52WW (1.22 )
Release Date: 08/27/2007
...

This is much more efficient than rebooting your machine and looking at
the POST output.