NIS 2005 - how do I reinstall?

Hi there, I have NIS 2005 on my laptop, which came pre-installed if I remember correctly. After a recent NIS update I have had big problems with emails. I seem to be able to receive now, but can't send whatever I try. I have disabled NIS and tried but nothing works. All the advice I am getting from elsewhere is that I should try uninstalling NIS, trying email to see if it works and then reinstalling to narrow down the problem. However it seems that there is no way of me downloading NIS 2005 again now to be able to reinstall it. Seems that only 2006 onwards can be re-downloaded. I have just paid for another year's worth of updates so don't want to ditch NIS - can anyone help please?

 

Incidentally, the email error message that started appearing since I last updated NIS is:

Your server has unexpectedly terminated the connection. Possible causes for this include server problems, network problems, or a long period of inactivity. Account: 'mail.talktalk.net', Server: 'smtp.talktalk.net', Protocol: SMTP, Port: 25, Secure(SSL): No, Error Number: 0x800CCC0F

 

I can confirm that I have changed no settings in my email, just updated NIS 2005. MY ISP has confirmed there are no problems with their mail server too.

 

Many thanks