USB flash drive - wireless networking (infrastructure)

I have 3 PCs (2 desktops and 1 laptop) all with Window XP Home Edition
1 desktop (Gateway) with Linksys Cable Modem with USB and Ethernet
Connections and Linksys Wirelss G Broadband Router
1 laptop (Dell) with Linksys wireless G adapter card
1 desktop (Dell) with Linksys Wireless G USB Network adapter
Gateway desktop and Dell laptop were "sort of"set up by Best Buy's
technician about a month ago, but he wasn't able to let these two machine
communicate with each other at all. Both were able to connect to the
internet. I somehow managed to share files and share printer.
Well, now I have a new Dell desktop and want to add this pc to the current
network. I already installed the wireless adapter in this new pc and tried
the XP's Network Set up wizzard and Wireless set up wizzard, but so far I
still can't see any computer in My network places. The problem is this:
During wirelss network set up, I was supposed to plug USB flash drive to
"access point" before I did the same with wireless laptop. Well, what I am to
do when the Linksys's Broadband router doesn't have USB flash drive "input?"
Unless I can overcome this problem, I am not going to be able to set up a
wireless network (infrastructure mode).
I read somewhere that you can "manually" do something to your access point,
but how?
Can someone help me with this? I am sure it's a common problem.
It seems much easier to set up a network if all the computers involved are
either all wireless or all wired.
Well, I sure could use somone's help here. I will really appreciate it.