How do I connect a Windows 8 laptop to a wireless network (which has a hidden SSID)?

The best way would be to tell your network administrator to turn on SSID broadcasting (undo the hidden SSID). This will improve security of the network and solve your problem in the same step.

Let me use an easy to image scenario:

With SSD broadcasting enabled there is someone a room. Every minute he calls out "Hi, I am SID, you can talk to me". With SSID broadcasting disabled he does not do this. Now I am going to talk to SID. Publicly I yell "Hi SID, this is Paul. Can you put this on the shell for me". Everybody still hears SIDs name and knows it is there. Telling SID not to shout his name every minute does not help to keep things hidden. As long as there is traffic the SSID of the network will be visible to everyone.

It gets worse. SID no longer shouts. Instead I sneak into the room and start shouting "Hi, I am SID, you can talk to me". This is not true, but heck, I can shout (broadcast) what I want. People start talking to me instead. I asked them for their passphases. People think they are authenticating to the real SID and give them to me. Security is compromised.

Imposing as SID should not work if I need to identify myself (read: use a certificate). However that is only the case if WPA2/Radius is used. (Your post mentions WPA-2 Personal, which not WPA 2 Radius).

Hiding the SSID was a sane advice when wireless was new and nobody had written a program yet to sniff the airwaves. These days you download such programs for free. (Heck, people sell kits which can do that for actually helping you to lay out your wireless networks transmitters in optimal places).

@Hennes - Can I ask you to add this information as the answer so I can upvote you/mark this as "the answer?" – Tonweight

Done, though I do not consider it a proper answer to the question. It is a solution. I think it is a good solution. But it does not answer the 'How do I connect to a a hidden SSID network in win-8' part.