Hi there
Windows XP often behaves strangely when sharing files with other computers.
The results I've found that usually work (I can't give ANY reason but over time this seems to do the trick I'm NOT a network guru -- this just works as I found by Trial and Error).
Before you start - SWITCH OFF DHCP --give each machine on your Network its OWN internal IP address. Also switch off any "Non computer" Network devices such as media stramers/ network disks /network printers etc as well. By Network disks I mean those one's that are stand alone network disks not "Shared disks " attached to computers on a LAN. You can switch these on again after you've got it all working.
I used to have NO end of problems with DHCP -- especially if you've got other devices such as those nice new stand alone Internet Radio devices, media streamers, network drives, network printers etc etc.
These "Non computer" devices can use an IP address that one of your machines is trying to use and you won't get an error message conflict.
Before you start :
On a Network it's better to DISABLE DHCP and assign each machine it's own IP address. You'll see the advantage of that too if you want to access a particular machine remotely OUTSIDE your network such as RDP etc.
Now :
1) Ensure the XP machine is in the same Network group name as the W7 machines such as MSHOME or WORKGROUP. If it is already then CHANGE to something else, re-boot, then CHANGE IT BACK again. This forces a total reset of Windows XP "Network Discovery".
2) The XP machine need to have a USER and PASSWORD set -- make it the same user and password as one of the W7 Machines in your network.
3) ensure file sharing is enabled on the XP machine -- if it is already DISABLE it, re-boot and then RE-ENABLE it again.
4) connect to the W7 machine file from XP via the IP address
\\192.168.x.x\D for example.
This will usually work -- Networking XP was ALWAYS a mega pain -- sometimes randomly ONE XP machine or other would suddenly become invisible to the network.
Connect FROM XP to W7 first and when that works you'll find the XP computer now mapped in the Network list on the W7 machine.
Cheers
jimbo
Added - if you DO have things like stand alone Internet Radio devices then you can in most Routers set DHCP to start at a specific IP address -- so still set your LAN computers to specific IP addresses (non DHCP) and allow your "Stand alone Network devices" to be assigned IP addresses via the Router's DHCP outside the range of your fixed LAN computers.
-J