Active Directory & group Policy change reporting

Hi,

I would like to know where I can obtain some kind of script that tells me what changes have occured in AD and GP, and who did it, where and when, etc.

I have been searching all over the internet for something like this but so far haven't really found anything. Ideally I want something like netwrix change reporter (which I have tried) but we cannot really afford these commercial auditing products as they are quite expensive. Hence the need for a script.

We have a full 2003 AD environment.

So can anyone point me in the right direction? And please don't post links to software sites that offer restricted feature trials etc :)

Thanks,

Taz