HELP !!! in tracking PPC

I'm still lost, I'm trying to find a way to track my ppc. I already using the "?" after the domain name to track the keyword, but I still did not figure out way to track the visitor. let me explain: I'm using : http://www.mydomain.com/index.html?=Keyword , now after the visitor enter the index page he/she fill a form and direct to a thank you page.sample
( index.html?=keyword (page a) -- FORM ( page B) ---> Thank you (page C).
how can I track which visitor from which keyword fill up the form and got to the Thank you page. I have and must use just one Thank you page. any suggestion , software which I can put to track it, I;m trying to find a solution but it seems that a lot of people has the same problem.

this might help you http://www.seochat.com/c/a/Website-...Ratio-Tracking/

That a good articel but still did not show me how to do it

Try to buy Mach5Gold and this is a web Analyzer, using this you can process your WebLogs and create an accurate WebStats for your site.

There you can easily check the conversion rates and the visitor FLOW from on page to another...

The tactic you are using is an effective one and using that URL Query you are able to track it from the Stats report..

did any one hear or using Opentracker.net