After another hour or two I can actually answer my own question.
Someone on another forum mentioned that you need to keep a mention of plain ol' localhost in the httpd-vhost.conf file, so here's what I ended up with in there:
<VirtualHost *:80>
ServerName localhost
DocumentRoot "c:/wamp/www/"
</VirtualHost>
<VirtualHost *:80>
ServerName platypus.dev
DocumentRoot "d:/projects/test/"
<Directory "d:/projects/test/">
Options Indexes FollowSymLinks Includes
AllowOverride All
Order allow,deny
Allow from all
</Directory>
</VirtualHost>
Exit WAMP, restart - good to go. Hope this helps someone else :)