You cannot access a shared folder that is located on a Windows 2000 or Windows 98-based computer from a Windows 7-based computer

You cannot access a shared folder that is located on a Windows 2000 or Windows 98-based computer from a Windows 7-based computer

Below link shows you how to solve this problem:
http://www.tannerwilliamson.com/2009/09/14/windows-7-seven-network-file-sharing-fix-samba-smb/

Please see the below screen shot:

There is another solution from Microsoft website:

http://support.microsoft.com/kb/982734