In 1.6.6. cannot select port (greyed out)

I am a noob and installed Arduino 1.6.6 on my Windows 7 64bit computer. Connected my Arduino Nano but in Tools-Ports, I cannot select a port as it is greyed out. I then ran the dpinst-86.exe and get an error saying "You have to run the 64-bit version on this machine". If I am not totally wrong, the dpinst-86.exe should include the 64-bit driver or not?

In the Device Manager the Nano was not recognized or just as "USB2.0-Serial". I tried to manually install it searching for drivers in "C:\Program Files (x86)\Arduino\drivers" but it also failed. Then I tried to install it from the list of manufacturers but under the three Arduino manufacturers, I could not find the "Nano".

Googling did not get me a lot further as the same problem was only described for Windows 8.1.

Any ideas what I have overseen or doing wrong?

I have kind of a similar problem! I am running an HP Computer AMD 64 Bit machine, Windows 7 Pro, that has a PCI Port card for Comm Ports 3 & 4 which I use to run Ham radios and Ham Modems! When I install Arduino Version 1.6.6 to my computer with the windows installer off the Arduino Web Site Downloads it automatically sets it up to the comm port card. This is verified in the Tools in 1.6.6 software. It let's you select 3 & 4 but greys comm port at top out and no other comm ports to change to. If I manually install from CD with Windows 7 Installer and unselect the USB driver not to be installed Automatically from Windows installer and go back and try to install it manually it does the same thing when running 64 bit diver exe file in the Drivers Folder. I want to use the (2) Arduino 2560s I bought!
This is my first experience with Arduino and it isn't looking good so far! I went as far as reporting a Bug Error which makes you sign up for some wacko web site and wants contributions! I'm not donating any money that these things won't even work to start with! When are we going to get help thru email I have listed in my sign up?
Sometimes Device Manager shows the so called port installed as unknown device in USB section and have had it under other sections too! To me this software needs to let you under the Tools have more choices namely adding the USB Selection! I'm Looking for Help to resolve this problem before I lose interest and go back to Parralax Propeller stuff!

Again I say we need help ASAP Please!

I could not find the "Nano".

The Nano typically uses a FTDI chip for its serial port. You can download the drivers from VCP Drivers - FTDI

Again I say we need help ASAP Please!

Start your own thread, don't hijack someone else's.

Same problem:Windows 10 (also on Win 7) Arduino IDE 1.64 or 1.83 both have grayed out PORT.
I can select the Trinket, I loaded and installed all the drivers but no luck.

Tried to find permissions in Win to access USB ports (just get TPC/IP port help)
Trinket spends very little time in Boot loader, I guess not enough time for Windoze to find a driver before it craps out with either unknown device or USB Serial 2.0 (whatever)

Any clear solutions out there?

Look at the chip near the USB. It will probably have "CH340G" on it. Google whatever is on that chip with "driver". As in "CH340G driver". Download and install the driver. This cured my problems with my knockoff board. My authentic board had no issues.