SP2 & BNU update

I have a MN500 and no wired computers connected at this
time. I have an intel notebook adapter and MN-510 on a
desktop which is setup in a different room than the cable
connection used for internet.

I finally updated to SP2 last night, and so far, no
problems connecting to internet or printer attached to
other computer.

I am getting the "Critical Updates...." message, but I
have not updated BNU because I wanted to see if there
were any problems out there, and it appears there is. I
also wanted to check on updating when I am not wired to
the MN-500 (the website for the update says you need a
wired connection for MN-700, no mention of the MN-500)

I keep seeing a post saying that the BNU isn't needed if
running XP. Is this true for all connected computers
even if none are wired to the MN-500? How do you manage
the network without it?

Thanks for your help.