1. In Windows 7:
1.1 Click the Start button and type secpol.msc then click OK
1.2 In Local Policies >> Security Options, double click on Network Security: LAN Manager authentication level to open it, then select Send LM & NTLM - use NTLMv2 session security if negotiated. Apply this setting.
1.3 Open Control Panel >> All Control Panel Items >> Network and Sharing Center >> Advanced sharing settings, in your current network profile, choose below options:
- Turn on network discovery
- Turn on file and print sharing
- Use user accounts and passwords to connect to other computers
1.4 Log off or restart Windows 7
2. In Windows 2003 / 2000:
2.1 Click the Start button and type gpedit.msc then click OK
2.1 In Computer Configuration >> Windows Settings >> Security Settings >> Local Policie >> Security Options, double click on Network Security: LAN Manager authentication level to open it, then select Send LM & NTLM Responses. Apply this setting.
2.3 In Run box, type gpupdate /force then OK to update new policy, OR restart Windows 2003
That's all. Now you can try to access your shared folders between Windows 7 and Windows 2003/2000.