The NetUserGetInfo function retrieves information about a particular user account on a server.

NET_API_STATUS NetUserGetInfo(
  LPCWSTR servername,
  LPCWSTR username,
  DWORD level,
  LPBYTE* bufptr
);

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/netmgmt/netmgmt/netusergetinfo.asp