Another way to do this, and this case it is probably the preferred method, is to not alter the httpd.conf file but rather do it in the .htaccess file instead. Add a line like this:
<BLOCKQUOTE><font size="1"face="Geneva, Verdana, Arial">code:</font><HR><pre><font size=1 face=courier>
AddHandler application/x-httpd-php .php3
</font>[/code]
The reason why changing the .htaccess file is better in this instance is that either is basically a hack, and it's better to localize (i.e. minimize) the effect of the hack to the root directory of the files in question. The httpd.conf has broader reach and the hack is likely to remain in place long after the .php3 files disappear from your server.