Why download a 3rd party proxy manager when windows netsh command line can do the trick? Few batch files should get you in order, just make sure when you make them you run them as Administrator.
You'll want to look at the netsh winhttp command set.
To view current proxy setting: netsh winhttp show proxy
To set a proxy server: netsh winhttp set proxy proxy-server="http=myproxy;https=sproxy:88"