Sorry, seems I wasn't clear in my original post.
My mobile wifi thingy is NOT a usb anything. If it was, I could probably use it on the desktop.
It's a little gadget with its own battery that sits on my desk, or in my pocket, or wherever, and magically connects with the Vodafone network, then broadcasts its own wifi signal that my laptop picks up. Voila! internet (but only for the laptop).
What I now want to do is connect the laptop and the desktop using my crossover cable, and have the desktop access the internet via the laptop.
Now: Vodafone network connects to wifi gadget connects to laptop NO CONNECTION to desktop.
I want: Vodafone network connects to wifi gadget connects to laptop connects (via crossover cable) to desktop.
Money is very tight, so even spending $20 is not an option.
Thanks again. Hope this clarifies matters a bit.