help to add a second ISP

hello everyone.
i running a mikrotik 750 with an ISP. the ISP has given me a modem that it is in bridge mode and i have the pppoe username/passwd in mikrotik, in port 2. All other ports are in the LAN segment and gets PAT to the pppoe. everything works smoothly for more that a year now and it is been upgraded to version 6.15
due to bandwidth issues i have in my office a second adsl line from a different provider. the modem is not in bridge mode and it gives me only a local LAN IP (192.168.45.2/24, with gateway 192.168.45.1[router]). this router is doing the PAT and i cannot change it, due to policy of the ISP.
i do need some help to configure the mikrotik to see the second ISP. i would like to loadbalance the traffic and connections such as torrents or multiple http connections to use both ISPs. could someone help me please since i am lost. i would appreciate if i could have this to be done through winbox, please.
my LAN is 192.168.17.0/24 with 192.168.17.1 being the router (mikrotik)

As far as I’m aware there’s no way to do any sort of effective load balancing over separate ISPs because a single stream needs to exist on one connection. The only way I’ve seen this effectively work is over tunnels across both ISPs to a router elsewhere and then to the Internet on a larger connection from there.

You can separate groups of machines and there is an example here: http://wiki.mikrotik.com/wiki/Load_Balancing_over_Multiple_Gateways