Im by no means any sort of expert on this, but the following setup works for me. in httpd-vhosts.conf, make sure the following line is uncommented.
NameVirtualHost *:80
The set up the virtual hosts:
<VirtualHost *:80>
DocumentRoot "d:/xaamp/htdocs/dev.somesite.com. au"
ServerName dev.somesite.com.au
</VirtualHost>
That works for me. I think you also need to define localhost as a vhost as well.
<VirtualHost *:80>
ServerName localhost
DocumentRoot "D:/xampp/htdocs"
</VirtualHost>
You can include per directory stuff as well by using
<VirtualHost *:80>
DocumentRoot "d:/xaamp/htdocs/dev.somesite.com. au"
ServerName dev.somesite.com.au
<Directory "D:/xampp/htdocs/dev.somesite.com. au">
Options Indexes Includes execCGI
AllowOverride None
Order Allow,Deny
Allow From All
</Directory>
</VirtualHost>
Then in the hosts file (from memory, in xp its found at c:\windows\system32\drivers\etc), define hosts like so:
127.0.0.1 localhost
127.0.0.1 dev.somesite.com.au