It isn't standard for tcp/ip.
somehow, someway your computer did a name query, and somebody answered it.
this could be a dns server, this could be a wins server, this could be another windows computer named my.
also, windows will append search domains when you don't use a fully qualified domain name (ie, you just use a hostname) in an attempt to resolve the name. it will also append .com and .net and .org.
The onlyway for you to really see what is happening is load up ethreal and then capture what is going on/who is resolving the name for you.