Two DSL's on a single PC

i have two DSL connection of 512 each is there any way that i can use both of them in a single PC i tried that i connect 2 DSL on two NICs but when i started using them only one out them is used (the LEDs of one DSL modems blink only while other remains silent mean they show no activity)

may be this is where the problem exists -- the gateway address for both the DSL modems is same i.e 192.168.1.1

even i tried that on VM ware to make use of each DSL separately in host and guest machines respectively but that shows the same behaviour only one out of two DSL modem shows activity please help me to find out the solution of the problem

two DSL but one PC is there any way that the connection could be bridged and both 512 connections combine to make a 1M connection

or

they could work separately , one in vmware guest machine and one in host machine

You can't use two network devices (routers or modems) with the same IP on the network - this may be the problem like you mentioned.

Set up both of them with different private networks e.g first one class B with gateway e.g 172.20.8.1 and other one class C e.g. 192.168.1.1

I'm not sure how internet browsers would use that connection but some programs are able to bind IP connection to their service.
Example - u could use P2P software or web server) to bind to IP 192.168.1.1 and use 172.20.8.1 for internet browsing.

The easiest method for you would be getting a dual WAN router - that would solve your all problems.