No Com port access on Dell Inspiron 17R after replacing win8 with win7  

Got new Dell Inspiron 17R 5737 w/win 8.1 and struggled for 2 months to get used to it without success so deleted in and reformatted hard drive. Installed win 7 ultimate x64. Updated all drives available from Dell site and also from 3rd party site. Everything is working EXCEPT that every time I plug an external device requiring a COM port, it simply does not work. I tried the USB2 and USB3 ports. The Wireless adapter is using COM 3-4-5-6 according to DEVICE MANAGER, and the indication I get when plugging in a USB cable while monitoring the DEVICE MANAGER, is 3 or 4 triangles with "!" in the center. Each of them displays a message under OTHER DEVICES: "AUDIO DEVICE ON USB BUS"; "ENHANCED COM PORT"; "STANDARD COM PORT"... when I open them I get the message "The drivers for this device are not installed (code 28). When I try to update or install a driver, it indicates that there are none available. I tried to connect the external device (a Yaesu FTdx3000 amateur radio transceiver with USB output) to each port with the same results. I do not have any other external device requiring a com port to see if different results would occur. However, I have confirmed that the radio communicates correctly using the USB2 port of my old Toshiba Quasimo using the same operating system. So the fault does not seem to be the cable or the radio, but, something in the Dell. HELP!

When you 'downgraded' from Win8.1 to Win7 did you check for Win7-compatible drivers at hhttp://www.dell.com/support/home/us/en/04?c=&l=&s=bsd? You'll need the Service Tag number, a label on the bottom of the computer or inside the battery compartment.