I am visiting my girlfriend's place in DC, and everyone has access to public networks made for the students in the intern program here. However, there is one network that she's been using that has the best connectivity in the building. She uses a Macbook but when I attempt to find the SSID in question, it doesn't show up on my HP G72 Laptop running Windows 7 Home Edition. Is there anything I can do to find this hidden network?

To find it? No, not easily. But you can create a manual connection to it - just copy the connection information from her Macbook and create a new wireless connection on your laptop using the same information. Be very careful though - there's a possibility, however slight, that if the connection isn't one of the school's approved ones that you're actually connecting to her neighbor's smartphone and running up their wireless phone bill. (Can you say 4G?)