PHP5 extension required to open in localhost

[Conjurer]

I installed XAMMP running on Windows XP Pro and it says everything is working.

I can open my regular htm files from localhost and I can open files that end with an extension of "php5."

But if the file extension is ".php" it doesn't want to open it in a browser, instead i get a dialog box that says: You are trying to open fileXyz.php which is a PHP Script - Open With ...

Choosing Firefox or Internet explorer - it doesn't open. If instead I change the extension to php5 then it recognizes it and opens in a browser just fine.

What setting would I need to tweak so that files ending in just ".php" will open in the localhost browser?

Thanks