I had a similar problem with my home network, which included:
Huawei HG520b ADSL wireless router
NAS network storage drive (wired connection to the router)
Medion tower computer with Win XP (SP3) Home edition (wired connection to the router)
HP laptop computer with Win XP (SP3) Professional (wireless connection to the router).
Networking had worked perfectly for several years between the Win XP computers - and also to the SMB server on the NAS network drive.
Very recently, I purchased a Samsung laptop computer with Win 7 (SP1) 64-bit Professional. I attempted to add the Samsung laptop to the network and discovered that I could access shared files on the Samsung computer from the XP computers
- but not vice versa. The Win 7 computer asked repeatedly for a Network Password, every time I attempted to access files on NAS drive or on the Win XP machines.
I tried everything mentioned in the previous posts including:
a. Turned on Network Discovery on the Win 7 computer
b. Turned on file and printer sharing on all computers
c. Turned on public folder sharing on the Win 7 computer
d. Turned off password protected sharing on the Win 7 computer
e. Disabled local account use of blank passwords to console login only (in local security policy/accounts)
f. Set Sharing and security model for local accounts as classic (in local security policy/Network access)
g. Synchronised that the system time and date on all machines
h. Ran the networking wizard on the Win XP machines (again)
None of the previous posts has mentioned KB922120, which includes an important Hotfix. The Hotfix enables Vista (and Win 7) computers to "discover" a Win XP machine. See
http://support.microsoft.com/kb/922120?wa=wsignin1.0.
I installed the Hotfix on both of my Win XP machines. This did enable the Win 7 computer to "discover" the Win XP machines - and included them in the network map.
Unfortunately, none of these steps provided a complete solution to the networking problem - and I never managed to access shared files on the HP Laptop or the NAS network drive - from the Win 7 computer.
Eventually, I devised the following tortuous "workaround" on the Win 7 computer, which did allow me to access shared files on the Medion tower computer:
1. Re-boot the Win 7 computer
2. Disable Network Discovery on the Win 7 computer
3. Enable Network Discovery on the Win 7 computer
4. Open Windows Explorer, select "Network" in the list of folders, and click on View / Refresh
However, this was not a satisfactory solution.
As a last resort, I replaced the Huawei router with a TP-Link TD-W8961ND ADSL wireless router - and discovered to my amazement that networking works perfectly with the new router. I cannot offer any a logical explanation, because I copied all of the network
and firewall settings from the Huawei router to the TP-Link device. Consequently, I would have expected the routers to operate in a similar manner. Maybe, there are significant differences in the firmware.
However, a Google search shows that many people have experienced similar problems, with very few documented solutions. For anyone who has been unable to establish networking between Win 7 and Win XP machines, it might be worth experimenting with a different
router. (That is in addition to the installation of Hotfix KB922120 and the steps (a - h) mentioned above.)