I currently have two different Internet connections: one is a 1 Mbps 3G connection (very low downtime but unstable bandwidth, fair latency, mobile, already NAT-ed at ISP-level, tethering allowed, 2 GB monthly allowance) and the other is a cheap 5 Mbps Cable connection (stable bandwidth but fairly high downtime, high latency, not NAT-ed, no allowance). I connect to the 3G network by means of tethering, with my phone acting as modem through Bluetooth, and to the Cable via a WiFi router.
I want to use both connections on the same computer but for different purposes at the same time. Specifically, I want to use the 3G connection for usual Internet activities like browsing, e-mail, IM and whatnot, and the Cable connection for bandwidth-intensive activities like large file downloads via HTTP and BitTorrent, video streaming and the likes.
How can I do this on Windows?