In Firefox the Information is saved in the file:
Code:
C:\Documents and Settings\[username]\Application Data\Mozilla\Firefox\Profiles\[randomletters].default\prefs.js
The proxy settings for Internet Explorer are stored in the registry under the following key:
Code:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\
or
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\