• connect to remote computer;
• iterate through the list of remote computer's logical disks
• filter only fixed drives (ignore mapped network drives, CDROMs etc)
• check the space available on the fixed drives.

• IPAdress may be address in the form "xxx.xxx.xxx.xxx", for example "169.254.112.1", or NETBIOS name of the computer.
• UserName should ne in the form "DOMAIN\Name". If this user name is local to the destination computer (not a domain name), then specify "COMPUTERNAME\name".
• Password is the password for the account used.

              
procedure CheckSpace(IPAdress, UserName, Password: string);
const
  ERR_MESSAGE = 'Drive %s has only %d bytes of free space';
var
  i: integer;
  vStorageInfo: TWmiStorageInfo;
begin
  // create the component on the fly.
  vStorageInfo := TWmiStorageInfo.Create(nil);
  try
    with vStorageInfo do
    begin
      // connect to remote computer 
      // When working with a local machine, all the 
      // parameters must be empty strings 
      MachineName := IPAdress;
      Credentials.UserName := UserName;
      Credentials.Password := Password;
      Active := true;

      // Iterate through the logical disks
      for i := 0 to LogicalDisks.Count - 1 do
      begin
        // Ignore mapped network drives;
        // Find disks with less than 10Mb free space.
        if (LogicalDisks[i].MediaType = MT_FIXED) and
           (LogicalDisks[i].FreeSpace < 10000000) then
         ShowMessage(Format(ERR_MESSAGE,
                            [LogicalDisks[i].Caption,
                             LogicalDisks[i].FreeSpace]));
      end;
    end;
  finally
    // Clean up.
    vStorageInfo.Free;
  end;
end;