Hi,
I am a bit of a newbie myself, but I am working on this problem right now.
I am using a Linux Dynamic DNS update client to keep my various domain names at DynDNS.org pointed at the dynamic IP provided by my ISP. Is this what you are trying to do?
I have been using
http://encodable.com/tech/eponym/ to do this.
It required some updates to my Perl setup - but it led me very carefully through this and was not an issue: in fact it will probably be useful elsewhere. I am struggling to automate it - but that is a result of me not knowing enough about how to set up rc scripts.
That said, if your windows machine is always on I don't see why it cannot do the job. The work is to touch the config on the DNS server itself at DynDNS. That is if you need the same thing as me.
Cheers
Tim.