All computers that I manage (at the office and home) are set to boot off
HDD, period. I don't want them to boot off an infected media.
I disagree, and think that the hard drive should be kept as first in
the boot sequence. You should change to some other device *only* when
you need to, and then change back again when you're done.
I say this for two reasons:
1. It takes care of the situation where a CD or diskette is
accidentally left in the drive, and trying to boot from it will
therefore fail.
2. A floppy accidentally left in the drive could be infected with a
boot-sector virus (these are less common than you used to be, but they
are still around); if so, and you boot from it, you will get infected.