can't change dir. to a mapped Drive in cmd

[MadSc13ntist]

I am aware that in Windows XP Home SP2 that if you try to change directory to a mapped network drive letter, the line runs and you are brought back to @HomeDir. This is not in the context of a script i am currently writting but i have yet to hear someone explain to me why this is? TechNet link? MSDN link? and i haven't found any knowledge base articles explaining it.

if anyone would be so kind as to explain this to me (you don't have to water it down) i would be very greatful.

I was asked this today and it bugged the $#!7 out of me that i didn't know for sure why.

Thanks in advance to all that reply.