Went BACK to the Linksys site, and after a lengthy conversation with a person named "Pooja Pawar" in their live chat thingy, the same conclusion I had earlier about reformatting the system was reached.
Then something popped into my tiny little brain. I suddenly remembered some problems I was having with the old Intel PC Pro webcam. It had trouble with drivers in the XP and Vista systems it has been used on, until I unplugged it from one USB port, then plugged it into a different one, then it worked perfectly. Soooo... making a long story short, I tried that with the wireless adapter on his PC. What'd ya know... instant internet access! If I had remembered that little thing several hours earlier (counting yesterday), I wouldn't have had to go through all that other hassle!
Only seems to work in the front USB ports though... doesn't function in neither of the 4 ports in the rear of the machine. Worked fine in the back until that "optional" Windows Update for the device.
The mysteries of life....