Bypass compulsory proxy or find proxy password on windows PC

[3.1415926]

Hi. I'm trying to hack a wifi network out of curiosity. I have already got access to the wifi password but there is a firewall which doesn't allow me direct access to the Internet. I'm required to connect via a http proxy which is used for web filtering.Is there any way to bypass the firewall and not use the proxy at all?
 
I think an easier way would be just to connect to the proxy. I can bear a bit of filtering. I have the IP address and port number but lack authentication details.

I have access to a computer which uses the proxy but I can't find a way to display the authentication details on the computer.  IE is the default browser but the internet options menu is blocked by admin.  I have downloaded Firefox with which the settings menu is available - the proxy settings are set to use 'system proxy settings'. Can't actually display these settings.

I'd like to be able to find these system settings and get the password from there. It has been suggested that these are stored in the registry but the regedit command is blocked by admin. Is there any way to access the system proxy settings? Could I write a program which reads these settings and prints the proxy username and password? If Firefox can access these settings then surely I could write a program to do the same.

Thanks in advance.

[mr.sinister]

you cold try a mitm attack to capture the data when your connected router

OR
gateway poison
ettercap with gateway poisoning enabled
plus a listener
nc -l -p 8080 -t
would record anything meant to be send to port 8080 on the router so might capture some details that way

OR

 i understand if you know they wifikey you can capure the wifi signal with some air sniffer program on a laptop and decode it with the known password. so it would be like a remote packet capture.
most wificards can at least record in a hacky way.

OR

a live disk like hirens bootdisk to lift/load  the registry hive from the pc you have access to and get a reg editor onto it .

hope this helps S