Computer Wrongly Identified on Network

Hello --

Need help on behalf of a friend, please. She has an XP and a Vista 64-bit
computer networked by means of a router. Her printer is also connected to a
router.

She is not particularly computer literate and is sometimes inclined to not
pay attention to what she is doing, so strange things happen.

Today a message appeared saying that all network drives could not be
connected and the icon bearing the name of her old computer (NTI-N1079) is
below the line, with an indication that it could not be connected.
Strangely, the properties for NTI-N1079 show it as Windows Media Player
instead of a computer on the network.

I'm thinking that if we can correct that problem, maybe she will again be
able to share her files between the two computers. How can we fix it so
that NTI-N1079 is properly recognized as a computer? And, how might it have
happened to start with?

Thanks.