Well if you were a administrator of the network you could use the web config.
From winproxy faq
|Q: How I can configure WinProxy?|
A: It is possible only via any WWW browser using URL connection to
But I'm taking a guess that your not the net admin for that place. Depending on the exact level of access and the network configuration you may be able to remove the proxy settings on the pc and static the workstation's address.
In some places avoiding the proxy is far more dificult where the router passes all web trafic through the proxy. Without reconfiguring the router, there is not much to go arround this <sometimes setting the workstation to access a public proxy may confuse the local proxy by using a diffrent port from standard web traffic>.
Do not damage or perminantly alter a machine that is owned/managed by someone else without thier permiton, doing so can get you removed from that location, thrown in jail, or worse.
If you disable the proxy in a public goverment funded location it may lead to the funding being removed from that location due to the child protection act.