Why doesn't ping -a resolve a hostname in XP?

Does anyone know why you cannot get a hostname using
ping -a on Windows XP? I can do it to my local machine
and get a resolution, but not any other computers on the
network. I have Windows NT 4 machines that do it just
fine on all subnets. Any ideas? I saw a previous response
to a similiar question posted and it commented on the PTR
record in DNS. I want to resolve the name from the
machine itself, not DNS.
To be totally clear, I have a network with no DNS or WINS
servers. I use PING -a and can not get a name resolved
using XP, but it works with NT. WHY?!?!?

TIA!