Configure windows xp and ubuntu linux to use two wireless nic's equally

How to configure windows xp and ubuntu linux to use two wireless nic's equally?

Well, when a remote site responds to a TCP/IP request, it responds to ONE ip not multiples.
For this to work, both signals would have to reach the remote site at the exact instant! (they wont!)
The remote site would have to respond at the exact instant. (It won't and can't.)
The signals would both have to reach back to you at the exact instant. (They won't and can't)

TCP/IP connections use IP addresses to respond to and two addresses get two responses not ONE. In your depiction you will be sending from TWO public IP's (one for each modem) not one! So the OS's only use ONE WAN connection at a time else you make for a large traffic jam!

You can "load balance" (use one when the other is busy) but you can't combine unless you get a bonded set of lines from your ISP (which basically is ONE LINE!)

Just the way TCP/IP works! If you need more pipe, get a bigger one don't try using two.