How to backup machinekeys?

I have Windows XP SP2 and Windows XP X64 on the same system. I use X64 to
back up the 32-bit version of XP and vice versa. I backup by copying to a
spare partition on a second hard driver.

Recently (after windows updates), there are crypto\...\machinekeys files
that can't be backed up. I don't encrypt any data, so do I even need these
files?