I just found the same issue with Aliases on a Windows install of Xampp.
To solve the 403 error:
<Directory "C:/Your/Directory/With/No/Trailing/Slash">
Require all granted
</Directory>
Alias /dev "C:/Your/Directory/With/No/Trailing/Slash"
The default Xampp set up should be fine with just this. Some people have experienced issues with a deny placed on the root directory so flipping out the directory tag to:
<Directory "C:/Your/Directory/With/No/Trailing/Slash">
Allow from all
Require all granted
</Directory>
Would help with this but the current version of Xampp (v1.8.1 at the time of writing) doesn’t require it.
As for op’s issue with port 80 Xampp includes a handy Netstat button to discover what’s using your ports. Fire that off and fix the conflict, I imagine it could have been IIS but can’t be sure.