network project help

hi im trying to make a little network IM in VB.net
and im runing into a few problems :P i made one in vb6 but i want to make one in vb.net so its fully compatible with windows 7
just wondering is there anyway to view the name of the user that is logged into a computer?
i have System.Net.Dns.GetHostName but that will only get me the name of the computer not the actuall user
thanks for the help and anyother questions i have i will put on here :P