I have just replaced XP with Server 2008 R2 on my test sever, and have been running 2008 R2 on my dev laptop. When my server was still XP, file sharing just worked, but now it just doesn't. I've enabled everything I can about sharing, and I can ping the server by machine name, but if I try an access a share, I get asked for a password. The passowrd dialog assumes a domain for this user, but neither my laptop admin user nor my server admin user can get past this login. What am I doing wrong?
Windows XP uses "guest only" file sharing, user accessing your file sharing will not be prompted for password. This kind of sharing although is convenience but introduce a dangerous security loopholes. In Windows Server 2003/2008, guest account is disabled and by default everything is disabled. You have to set NTFS, create share permission and more... Good luck.
Have you set permissions for the share and NTFS permissions on the folder/files?
The fact that it is prompting you, means its probably working fine, just a perms/settings conflict.
The "standard practice" if you like, is to allow full access to "domain users" in the sharing, and selective permissions on the actual NTFS objects for more granular control. (Like some users no access to certain folders, others read only, others read/write, others append only etc.. you just can't do that with the sharing tool, but you can with NTFS, and you can use groups!)
If you can't get it, you can always enable auditing, it will quickly fill your security event logs with who/why.
Also, if you try several times, your account may get locked out, so check that too!