I am running Windows 7 Professional and Windows 7 Ultimate on two different PSCs, When I installed the OS I was able to connect to all shares on my network but as of Monday 10/26/09, I cannot connect to a machine running Windows 2000 server (called Delta). I can connect to Delta from my Windows XP machines but not from the Windows 7 machines. I get a Windows Security panel asking for User Name and Password, I put in the proper ID but panel still says Login failure: unknown user name or bad password. . Any help will be appreciated.

I don't know if this is possible, I think you have to use higher version of NTLM on Windows 2000.

Here are reference links: How to enable NTLM 2 authenticationFile and Printer Sharing in Windows Vista (Section: Cannot Authenticate to a Shared Folder from a Windows Vista-based Computer)Hope it helps.