<<< I have installed the BT Voyager Wireless Adapter software on the laptop and connected the Adapter to the desktop via the USB lead >>>
I don't follow this - or do you mean you have installed the software in the *desktop* PC and plugged a USB wireless adapter into it?
You don't need a floppy drive, or a pen drive or anything else to set up additional computers in the network. Set any folders that you want to have available over the network as "shared" by right clicking and selecting the Sharing & Security option. At least one folder should be "shared" in each PC. Any firewall software needs to be configured to allow access to the networked computers, which may involve adding their IP addresses in a trusted section.