Okay, now that I was directed to where the drivers were located, I ran "dpinst-amd64.exe." After the installation, my system indicates it has
Arduino Srl (www.arduino.org) Arduino USB Driver (02/27/2014 22.214.171.124)
Arduino LLC (www.arduino.cc) Arduino USB Driver (01/04/2013 126.96.36.199).
Both are marked as ready to use. When I plug the Arduino into a USB port, nothing obvious happens. When I bring up the IDE, the port option is grayed out, and the Device Manager doesn't even have the Port group listed. Of course, trying to upload a sketch fails. I have tried this on an older original Arduino UNO and a new SainSmart MEGA, and both fail.
Just now I removed a new original UNO, made in Italy, fresh from the box and I get the same response. No port assignment and a failed upload.
This is all done on an HP machine running Windows 7 Ultimate with 12MB of memory. I had previously used the Arduino IDE on Windows XP and everything had worked fine, but, alas, I don't have any machines running WinXP.
My computer is of the 64-bit variety, but on a whim I tried installing the 32 bit version of the IDE. I was quickly told to use the 64-bit version instead.
If anyone has any ideas on this issue, I would like to hear from them.