Problems with php contact form

Hi guys, right I followed the php contact form to what I believe to be an almost exact replica. The form text is in a htm file and the php code is in a file called mailer.php

When the form is submitted, I get an error screen that says all of this:

[SIZE=1]*"Notice: Undefined index: radio in \NAS40ENT\domains\b\bluechipmc.co.uk\user\htdocs\mailer.php on line 9

Notice: Undefined index: drop_down in \NAS40ENT\domains\b\bluechipmc.co.uk\user\htdocs\mailer.php on line 10

Notice: Undefined index: check in \NAS40ENT\domains\b\bluechipmc.co.uk\user\htdocs\mailer.php on line 12

Warning: Invalid argument supplied for foreach() in \NAS40ENT\domains\b\bluechipmc.co.uk\user\htdocs\mailer.php on line 12

Notice: Undefined variable: check_msg in \NAS40ENT\domains\b\bluechipmc.co.uk\user\htdocs\mailer.php on line 16
Data has been submitted to mr-celica@hotmail.co.uk!
Warning: mail() [[/SIZE][SIZE=1][COLOR=#0066cc]function.mail[/COLOR][/SIZE][SIZE=1]]: “sendmail_from” not set in php.ini or custom “From:” header missing in \NAS40ENT\domains\b\bluechipmc.co.uk\user\htdocs\mailer.php on line 19"*[/SIZE]
[SIZE=1][/SIZE]
Here is a link to the page itself so you can see for yourself:
http://www.bluechipmc.co.uk/message.htm
Just enter anything in the fields and click submit to see the error page.

Please can somebody here help? I’ve tried a search on the forum, but most of the threads seem to be about making this work in a flash file.

Cheers, Ron