A lot of this depends on the operating system for ease or if it is even possible.
I cannot speak to such an application under Windows in any flavor.
I can vouch for it under Unix, and then by implication it MAY be possible under Linux. But I should qualify this further with I have seen multiple network ties hosted under a single machine, neither wireless nor to be unified at some point - each required separate sessions. But that was also the goal we pursued, so....
But it wasn't trivial to set up under Unix - I suspect (with NO basis for this opinion) that it would be difficult to impossible with Windows unless they anticipated the need.
But you may find the web has something available for $19.95 out of the box, because the web is a wonderful place!
Rereading this all before posting - I realize I have enough disclaimers as to make it useless to you - so Off-Topic for me!
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"If you want to get somewhere else, you must run at least twice as fast as that!"
Longer answer, Your computer will only address one wireless card at a time, and the data through put rate would be dependant on the either your wireless provider, or the wireless modem/hub attached to your ADSL line.
Also you could cause contention issues either in your PC or in the modems by trying to have the same MAC address on both wireless cards.
They do run multiple wireless cards on servers to spread the network load but the individual PC's on the network are addressed to their particular "port"
Hope that helps.
P.S. How's the mower?
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There are two reasons for a man to do a thing, One that sounds good, and the real one...
Which one of the mowers?
I only have 6 :D
Oh right, the engine that couldn't throttle on choke?
That is kinda in the sidelines @ the mo, I have given up with that engine for a while and have just finished making one good mower out of a load of bits and bobs that I have had lying around such as an old body, old engine, etc.
Thanks for the interest
Wireless cards are usually not the speed limiter when using the internet. The internet bandwidth is. Even the slowest wireless cards (unless you're using quite a few computers at once on the same router) outrun all personal internet speeds. The exception is if you have poor signal strength, which can slow wireless to a crawl. If this is the case, try switching to wireless N .