Sudden problems with networking,

I installed my microsoft MN 720 wireless network card,
and everything was working great, installed an Actiontec
gateway for all my computers to connect to the internet
and network them. for the first week everything was fine,
i could transfer files between the computers easily
dragging and dropping with no problem. then all of a
sudden the other computers werent showing up on the
network as computers, just as unknown devices that i
could not access. i have tried reinstalling my software,
system restoring to a date where i knew the transfer was
all working and i got it working once. but since then i
have had no luck. Both the other 2 computers on the
network are on a network called Homes whilst i am on
MSHOME2. I have no idea how i fix this and would like to
transfer all my files so i can restore this computer to
its factory settings. All pcs are running XP home OS and
nothing was changed on any of them between it working and
then not working