If you are just talking about viewing the page locally within your home network, you don't need to turn on OSX's built in webshare. MAMP can share pages perfectly fine, you just need to punch in your mac's ip adress from the PC, and then the port number for MAMP, as far as i recall it runs on a port 8888, so you would have to punch in for instance 192.168.1.10:8888 in the PCs browser