Error 500 during mult site install on Apache on Windows 8

I am new to Drupal. I am installing Drupal 7 on my Windows 8 PC on which is already WAMP so that I may experiment.

I know that I will be building several sites on one server and so decide to opt for multi site, sharing code base but separate MySQL databases.

The base Drupal installation went well. I put the installation in C:\wamp\www\drupal. I just access the site with localhost and the drupal subdirectory.

Then I set up a test domain www.playdrupal.com in my hosts file. I also set up virtual hosts by uncommenting the line in httpd.conf file (Include conf/extra/httpd-vhosts.conf) and added the following lines to httd-vhosts.conf file:

NameVirtualHost *:80 

<VirtualHost *:80>
    DocumentRoot "c:/wamp/www/drupal"
    ServerName www.playdrupal.com
    ServerAlias playdrupal.com domain
    ErrorLog "c:/wamp/www/drupal/logs/playdrupalcom-error.log"
    CustomLog "c:/wamp/www/drupal/logs/playdrupal.com-access.log" common
</VirtualHost>

<VirtualHost *:80>
    DocumentRoot "c:/wamp/www"
    ServerName localhost
    ErrorLog "logs/error.log"
    CustomLog "logs/access.log" common
</VirtualHost>

I then created the folder playdrupal.com in the sites folder of the Drupal installation and copied the default.settings.php from the default folder to the new folder and renamed it settings.php.

I then created a new database and user to manage it.

When I went to www.playdrupal.com in IE 10 (Desktop) it started the install script got to the page to key in the database name, user and password. After that I got the 500 error. In the error log it mentioned a syntax error. I found this in the new site's settings.php where it was merging the database details of the two sites and creating a syntax error in the process.

I found that the default.settings.php file had the first site's database settings, so I had been copying this into the new settings.php file.

So I edited the default.settings.php to its original state and re- copied it to the second site's settings.php.

The database had not had any tables created so I tried again. Now it gets to the page for keying the site name and administrator username and password. After that I get the 500 error and the error log says:
Fatal error: Call to undefined function node_types_rebuild() in C:\\wamp\\www\\Drupal\\includes\\common.inc on line 7475, referer: http://www.playdrupal.com/install.php?profile=standard&locale=en&op=star...

I really am lost now and searching these forms did not present a solution. I have also read all the installation pages, including multi-site in the Drupal documentation.

Any further ideas would be much appreciated.

Thanks