T> Where do I add my new sender id and what file do I use?

<URL:http://www.microsoft.com./mscorp/twc/privacy/spam_senderid_itpro.mspx>

T> Also when I add this to my domain do I need to supply the sender id
to my ISP as well?

How are we supposed to know?  We don't know what your domain name is,
nor who publishes your DNS data, nor who your ISP is for that matter.

T> And by me adding this record to my server, will this have any effect
on mail?

Yes.