Howdy, ok the error means that php is not configured properly to access your current database program...
First things first... as far as I know (I may be wrong).. all of your php scripts MUST be in your webpage directory... ex:
in your c:\inetpub...\wwwroot OR something similar to that...depending on what kind of webserver program you are using... in my example it's IIS.
I'm not sure how you set up php/webserver/database so here's a link that will do all three for you.. and it should work find...
http://www.firepages.com.au/phpdev.htm
Rgds,
Swixy