WORKAROUND SUCCESSFUL!!
To recap, my network consists of 3 xp machines hard wired, 1 xp wireless and 1 win 7 wireless attached to a netgear router. Am using WEP wireless security with a 26 digit hex code. From Christmas '09 'til about the middle of June this setup acted as a normal network. One of the XP machines I use as a print server for a Samsung Laser printer, another is a print server for an Epson color printer and the other wired xp is my has a large USB external drive connected--that I back up all pcs to using xcopy and/or robocopy.
During the above period I was able to do normal sharing and mapping of all the computers files and resources. Each computer could see all the others in windows explorer.
Then, with no changes to the network on my part, windows 7 went stealth and blind. The XP machines could not see it and it could not see the XP machines. I been googleing and trying various suggestions but nothing seemed to work. I disconnected all but one XP and the Win 7 machine from the network. Swapped routers, changed network names. Added IPv6 protocol to xp adapters. Removed all vestiges of security suites on these 2 computers and took down their windows firewalls. Still, they couldn't see each other.
Each was able to ping the others Ip address. Something may have clicked from one of the numerous posts I've viewed over the last month so here is the workaround.
*********************WORKAROUND!!
On win 7 machine I mapped the IP address plus folder to a drive letter e.g.
\\192.168.1.10\c\mine and sure enough I was able to access that folder on the XP machine. Did the same for the XP machine mapped
\\192.168.1.11\users\public and it also worked. Now for the printer, after trying various things I found that going to the Win 7 Devices & Printers>add network printer "Click on Printer Not Shown" in shared printer by name enter the ip address of your XP printserver. Mine is
\\192.168.1.10\SamsungM and sure enough it connects and is printing. To further test, I did the same for the IP address of the XP machine that has the epson. It works tonight. CAUTION!! One thing working for me in this workaround is the ability of my router to reserve and IP address for a particular computer name & mac address.
The XP with the laser and the win 7 laptop are shut down each evening. Will only post again if it doesn't work tomorrow, or if win 7 suddenly works with the network in a NORMAL manner.