So you have PHP and MySQL installed now but your local copy of Wordpress just isn't wanting to play ball....
Well it turns out that you need to make a few changes to your php.ini file.
if you do a search for extension=php_mysql.dll and un comment it ie delete the ; at the beginning of the line
then search further up in the ini file for extension_dir="./" and replace ./ with c:\php\ext (assuming your php is in c:\php) so it will look like: extension_dir="c:\php\ext". This tells php that the dllfor the php_mysql.dll is located in c:\php\ext.
save your php.ini
Also copy libmysql.dll from c:\php c:\windows\system32 and then restart IIS.
you should now be able to use wordpress from your local PC.