vista, xp, network, problem

Hi
I have had no luck trying to get vista to network with my xp machine ever
since I installed vista.
I have tried every suggestion I found here, in this newsgroup and in vista's
help, with no luck.
Sometimes, after I change the workgroup name from MSHOME to WORKGROUP or
from WORKGROUP back to MSHOME I see the xp machine showing up in in network
center (NC) while NC is opened. When I close NC and re-open it the xp machine
is no longer there.
While the the xp machine is the in the NC, if I try to open it I either get
a "network path cannot be found" or "Access is denied" messsage.
If I run the diagnostic tool it reference to something about a wireless
network.
Neither computer have any problem connecting to the internet via my router,
but to each other - no luck.
My install was done as an upgrade over XP.
Also, AOL is not working. I even uninstalled AOL's Port Magic without any
luck with my home network. And when I tried to reinstall AOL's Port Magic
vista would not let me.
Any suggestions