My husband's Dell laptop runing XP Pro has been part of a home network we have had for about a year. He had no problem before printing wirelessly to our HP DSC 2400 All in One printer. However, several days ago (15 Sept. 2005), he could no longer access our hard-wired computer, the HP Media Center m470n desktop running XP Pro.
The symptoms:

1. The computer would not show up in My Network Places in his Windows Explorer. His computer could not find any of the folders (C Drive and My Documents) that we had designated as shared on the HP desktop.

2. He could no longer access the printer. He inadvertantly uninstalled the HP printer from his Printers and Faxes list. When he tries to use the Add New Printer Wizard, the HP printer will not show up on the list of computers on the network.
3. Once or twice the printer did show up on the list of computers, but it asked for him to enter a username and password. He never had used a password before. "Guest" was displayed on this, but was "grayed out."

Other facts:
--All of our computers are in the same workgroup, MSHOME.
--His computer can ping the HP desktop, and the HP desktop can ping his computer.
--I can access his computer by typing its IP address into the Run command line box.
--We have a cable modem by Scientific-Atlanta; our ISP is Comcast. We have wireless networking with a LinkSys router.
--My husband can still access the Internet just fine through the wireless router.
--There is no firewall set on the HP computer right now.