nobleone

Hello i have a problem with my network. Coz i got 2 PC with NT OS and one with XP, the modem that i use is a speed Touch 500 with ASDL, so it got 4 RJ45 ports and all PC got it own port, i can surf with all PC's on the internet, and i can see all files from each PC with NT OS. but i can't see the XP one the network grup. But from the XP PC i can see the PC's with NT OS, but i can not enter coz it ask me for password. But why if between the NT i can enter without any password Thanks