According to Google, you can’t have more than one AdSense account. However it is possible for you to have more than one AdSense web site for your Google AdSense Account. Having more than one AdSense web site for AdSense account does not violate Google terms and conditions. You don’t even have to inform Google about your new AdSense web site because Google will automatically detect the new site. In fact, the more AdSense web sites you have displaying Google AdSense ads, the more money you will make. However, you must make sure that any new site you add, it must conform to Google AdSense Program policies.
For your new AdSense web site, all you have to do is copy and paste the same ad layout code you previously copied and pasted to your original site. The same rules apply when adding an AdSense for Search box to your new site. Simply choose all the parameters from the choices displayed, copy the code to the new site or new pages within the old site.