An addendum to my original solution to getting Joomla 3.0 to install.
The following is a multiple step solution to
1. Install
2. Turn Magic Quotes off

Step 1.
Copy your Joomla 3.0 folders to your webhost
Create a php.ini file with the following lines:

magic_quotes_gpc = Off
session.save_path = "/tmp"

Copy the php.ini file to your /installation subfolder on your webhost.
(You may or may not need the session.save_path line and you might need to edit it for the specific location of the /tmp folder on your webhost)

Now you should be able to go to your browser , open your website and have Joomla think magic quotes is off. (It isn't really, but this will let you install at least.)
Proceed with your install.

Go to the root folder of your website and create a php.ini file
Add the following lines:

magic_quotes_gpc = Off
magic_quotes_runtime = Off
magic_quotes_sybase = Off

Next we need to edit/create a .htaccess file in the root directory
it should have the following line:

SetEnv PHPRC /path /to/php.ini

The path will vary depending on your webhost
For example on my own site it is set as follows:

"SetEnv PHPRC /home/username/public_html/php.ini" where the username is my cpanel username.

Now for the usual problems.
If you create a php.ini file or a .htaccess file in some editors, be aware they may add an extension to the filename.

Make sure php.ini ISN'T really php.ini.txt for example.
And don't forget the "." in front of the .htaccess

I hope this guide helps someone struggling to get Joomla working.
Hang in there, it is well worth the effort.