You can install Yahoo messenger 8 from yahoo, but yahoo forces you in such a way that you need to download a small setup file, which does the live streaming installation. It is really hard to install yahoo mesenger in such a way for dial up users, all the data goes when disconnection occurs.

Now, you can download the full standalone installer from yahoo itself from http://download.yahoo.com/dl/msgr8/us/ymsgr8us.exe

Download the above setup file from yahoo (10mb+), and install it following the so given instructions.