I'm trying to access a Windows 8 station HDD with \\<IP>\c$ and it keep bumping me for user/pass.
I disabled UAC and changed to local user, still the same.
Added password to the user also.
Are you authenticating using the device name as the Domain? IE
PCName\User.
If you skip the Domain portion it's going to attempt to authenticate using the device you are accessing it from which wouldn't work unless you specifically allowed for it in the security tab of the C drive on the device you are wanting to access.